// Numbas version: exam_results_page_options {"name": "Quadratic Equations: The Quadratic Formula (Instructional)", "metadata": {"description": "

Identify co-efficients, then use quadratic formula to find roots.

\n

All set to be distinct and real. Some can be non-integer (0.5 steps)

", "licence": "Creative Commons Attribution 4.0 International"}, "duration": 0, "percentPass": "80", "showQuestionGroupNames": false, "shuffleQuestionGroups": false, "showstudentname": true, "question_groups": [{"name": "Group", "pickingStrategy": "all-ordered", "pickQuestions": 1, "questionNames": ["", ""], "variable_overrides": [[], []], "questions": [{"name": "Quadratic Equations: The Quadratic Formula 01", "extensions": [], "custom_part_types": [], "resources": [], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "contributors": [{"name": "Michael Proudman", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/269/"}], "tags": [], "metadata": {"description": "

Solve quadratic equations (non-simple case, two real, discrete integer roots) using the formula.

", "licence": "Creative Commons Attribution 4.0 International"}, "statement": "

If we have a quadratic equation of the form  \\( ax^2 + bx +c = 0 \\),  we can use the Quadratic Formula:

\n

 

\n

\\( \\LARGE x= \\frac{-b \\pm \\sqrt{b^2 -4ac}}{2a} \\)

\n

 

\n

to find the roots of the equation. (Note the plus-or-minus means there are two solutions, not just one.)

\n

It is also sometimes known as Shreedhara Acharya's formula, named after the 10th century Indian mathematician who first derived it.

", "advice": "

We are asked to find the roots of various quadratic equations using the Quadratic Formula. To enable us to do this, we are first asked to identify the co-efficients  \\( a \\), \\( b \\) and \\( c \\) each time.

\n

\n

a)

\n

\\( \\simplify{ {a1}x^2 + {b1}x + {c1} } =0 \\)

\n

The co-efficients of this equation can simply be read from the equation, taking care to take account of positive and negative values:

\n

\\( a = \\)  \\( \\var{a1}\\)     \\( b = \\)  \\( \\var{b1}\\)   and  \\( c = \\)  \\( \\var{c1}\\)

\n

We now write the equation substituting these values in the correct places and, again, being careful with any negative values:

\n

\\( x= \\frac{-b \\pm \\sqrt{b^2 -4ac}}{2a} \\)     becomes     \\( x= \\frac{-(\\var{b1}) \\pm \\sqrt{(\\var{b1})^2 -4 \\times (\\var{a1}) \\times (\\var{c1})}}{2 \\times (\\var{a1})} \\)

\n

Simplify this as much as possible (mainly the expression inside the square root and the denominator):

\n

\\( x= \\frac{\\simplify{-{b1}} \\pm \\sqrt{\\simplify{{b1}^2 -4*{a1}*{c1}}}}{\\simplify{2{a1}}} \\)

\n

Now, carry out this calculation twice, first using the plus (\\( + \\))  and then using the minus (\\( - \\)).

\n

This will give you the two roots:    \\( x = \\var{x1} \\)  and   \\( x = \\var{x2} \\)

\n

 

\n

 

\n

b)

\n

\\( \\simplify{ {a2}x^2 + {b2}x + {c2} } =0 \\)

\n

The co-efficients of this equation can simply be read from the equation, taking care to take account of positive and negative values:

\n

\\( a = \\)  \\( \\var{a2}\\)     \\( b = \\)  \\( \\var{b2}\\)   and  \\( c = \\)  \\( \\var{c2}\\)

\n

We now write the equation substituting these values in the correct places and, again, being careful with any negative values:

\n

\\( x= \\frac{-b \\pm \\sqrt{b^2 -4ac}}{2a} \\)     becomes     \\( x= \\frac{-(\\var{b2}) \\pm \\sqrt{(\\var{b2})^2 -4 \\times (\\var{a2}) \\times (\\var{c2})}}{2 \\times (\\var{a2})} \\)

\n

Simplify this as much as possible (mainly the expression inside the square root and the denominator):

\n

\\( x= \\frac{\\simplify{-{b2}} \\pm \\sqrt{\\simplify{{b2}^2 -4*{a2}*{c2}}}}{\\simplify{2{a2}}} \\)

\n

Now, carry out this calculation twice, first using the plus (\\( + \\))  and then using the minus (\\( - \\)).

\n

This will give you the two roots:    \\( x = \\var{y1} \\)  and   \\( x = \\var{y2} \\)

\n

 

\n

 

\n

c)

\n

\\( \\simplify{ {a3}x^2 + {b3}x + {c3} } =0 \\)

\n

The co-efficients of this equation can simply be read from the equation, taking care to take account of positive and negative values:

\n

\\( a = \\)  \\( \\var{a3}\\)     \\( b = \\)  \\( \\var{b3}\\)   and  \\( c = \\)  \\( \\var{c3}\\)

\n

We now write the equation substituting these values in the correct places and, again, being careful with any negative values:

\n

\\( x= \\frac{-b \\pm \\sqrt{b^2 -4ac}}{2a} \\)     becomes     \\( x= \\frac{-(\\var{b3}) \\pm \\sqrt{(\\var{b3})^2 -4 \\times (\\var{a3}) \\times (\\var{c3})}}{2 \\times (\\var{a3})} \\)

\n

Simplify this as much as possible (mainly the expression inside the square root and the denominator):

\n

\\( x= \\frac{\\simplify{-{b3}} \\pm \\sqrt{\\simplify{{b3}^2 -4*{a3}*{c3}}}}{\\simplify{2{a3}}} \\)

\n

Now, carry out this calculation twice, first using the plus (\\( + \\))  and then using the minus (\\( - \\)).

\n

This will give you the two roots:    \\( x = \\var{z1} \\)  and   \\( x = \\var{z2} \\)

\n

\n

\n

\n

", "rulesets": {}, "builtin_constants": {"e": true, "pi,\u03c0": true, "i": true}, "constants": [], "variables": {"a1": {"name": "a1", "group": "Question A", "definition": "random(2..9)", "description": "", "templateType": "anything", "can_override": false}, "x1": {"name": "x1", "group": "Question A", "definition": "random(-9..9 except 0 except 1 except {a1})", "description": "", "templateType": "anything", "can_override": false}, "x2": {"name": "x2", "group": "Question A", "definition": "random(-9..9 except 0 except 1 except {a1} except {x1})", "description": "", "templateType": "anything", "can_override": false}, "b1": {"name": "b1", "group": "Question A", "definition": "-{a1}*({x1}+{x2})", "description": "", "templateType": "anything", "can_override": false}, "c1": {"name": "c1", "group": "Question A", "definition": "{a1}*{x1}*{x2}", "description": "", "templateType": "anything", "can_override": false}, "plus": {"name": "plus", "group": "Trial check", "definition": "(-{b1}+sqrt({b1}^2-4*{a1}*{c1}))/(2*{a1})", "description": "", "templateType": "anything", "can_override": false}, "minus": {"name": "minus", "group": "Trial check", "definition": "(-{b1}-sqrt({b1}^2-4*{a1}*{c1}))/(2*{a1})", "description": "", "templateType": "anything", "can_override": false}, "a2": {"name": "a2", "group": "Question B", "definition": "random(2..9 except {a1})", "description": "", "templateType": "anything", "can_override": false}, "y1": {"name": "y1", "group": "Question B", "definition": "random(-9..9 except 0 except 1 except {a2})", "description": "", "templateType": "anything", "can_override": false}, "y2": {"name": "y2", "group": "Question B", "definition": "random(-9..9 except 0 except 1 except {a2} except {y1})", "description": "", "templateType": "anything", "can_override": false}, "b2": {"name": "b2", "group": "Question B", "definition": "-{a2}*({y1}+{y2})", "description": "", "templateType": "anything", "can_override": false}, "c2": {"name": "c2", "group": "Question B", "definition": "{a2}*{y1}*{y2}", "description": "", "templateType": "anything", "can_override": false}, "a3": {"name": "a3", "group": "Question C", "definition": "random(2..9 except {a1} except {a2})", "description": "", "templateType": "anything", "can_override": false}, "z1": {"name": "z1", "group": "Question C", "definition": "random(-9..9 except 0 except 1 except {a3})", "description": "", "templateType": "anything", "can_override": false}, "z2": {"name": "z2", "group": "Question C", "definition": "random(-9..9 except 0 except 1 except {a3} except {z1})", "description": "", "templateType": "anything", "can_override": false}, "b3": {"name": "b3", "group": "Question C", "definition": "-{a3}*({z1}+{z2})", "description": "", "templateType": "anything", "can_override": false}, "c3": {"name": "c3", "group": "Question C", "definition": "{a3}*{z1}*{z2}", "description": "", "templateType": "anything", "can_override": false}}, "variablesTest": {"condition": "", "maxRuns": 100}, "ungrouped_variables": [], "variable_groups": [{"name": "Trial check", "variables": ["minus", "plus"]}, {"name": "Question A", "variables": ["x1", "x2", "a1", "b1", "c1"]}, {"name": "Question B", "variables": ["y1", "y2", "a2", "b2", "c2"]}, {"name": "Question C", "variables": ["z1", "z2", "a3", "b3", "c3"]}, {"name": "Unnamed group", "variables": []}], "functions": {}, "preamble": {"js": "", "css": ""}, "parts": [{"type": "information", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null}, {"type": "information", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "

For the following equations, first identify the co-efficients, then use the formula to calculate the roots:

"}, {"type": "gapfill", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": false, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "

\\( \\simplify{ {a1}x^2 + {b1}x + {c1} } =0 \\)

\n

The co-efficients of this equation are:

\n

\\( a = \\)  [[0]]   \\( b = \\)  [[1]]   and  \\( c = \\)  [[2]]

\n

 

\n

Now use the formula to find the roots:

\n

\\( x_1 = \\)  [[3]]

\n

\\( x_2 = \\)  [[4]]

\n

(If you are sure that your roots are correct but they are marked wrong, switch them around).

", "gaps": [{"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{a1}", "maxValue": "{a1}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{b1}", "maxValue": "{b1}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{c1}", "maxValue": "{c1}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{x1}", "maxValue": "{x1}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{x2}", "maxValue": "{x2}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}], "sortAnswers": false}, {"type": "gapfill", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": false, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "

\\( \\simplify{ {a2}x^2 + {b2}x + {c2} } =0 \\)

\n

The co-efficients of this equation are:

\n

\\( a = \\)  [[0]]   \\( b = \\)  [[1]]   and  \\( c = \\)  [[2]]

\n

 

\n

Now use the formula to find the roots:

\n

\\( x_1 = \\)  [[3]]

\n

\\( x_2 = \\)  [[4]]

\n

(If you are sure that your roots are correct but they are marked wrong, switch them around).

", "gaps": [{"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{a2}", "maxValue": "{a2}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{b2}", "maxValue": "{b2}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{c2}", "maxValue": "{c2}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{y1}", "maxValue": "{y1}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{y2}", "maxValue": "{y2}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}], "sortAnswers": false}, {"type": "gapfill", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": false, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "

\\( \\simplify{ {a3}x^2 + {b3}x + {c3} } =0 \\)

\n

The co-efficients of this equation are:

\n

\\( a = \\)  [[0]]   \\( b = \\)  [[1]]   and  \\( c = \\)  [[2]]

\n

 

\n

Now use the formula to find the roots:

\n

\\( x_1 = \\)  [[3]]

\n

\\( x_2 = \\)  [[4]]

\n

(If you are sure that your roots are correct but they are marked wrong, switch them around).

", "gaps": [{"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{a3}", "maxValue": "{a3}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{b3}", "maxValue": "{b3}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{c3}", "maxValue": "{c3}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{z1}", "maxValue": "{z1}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{z2}", "maxValue": "{z2}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}], "sortAnswers": false}], "partsMode": "all", "maxMarks": 0, "objectives": [], "penalties": [], "objectiveVisibility": "always", "penaltyVisibility": "always"}, {"name": "Quadratic Equations: The Quadratic Formula 02", "extensions": [], "custom_part_types": [], "resources": [], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "contributors": [{"name": "Michael Proudman", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/269/"}], "tags": [], "metadata": {"description": "

Solve quadratic equations (non-simple case, two real, discrete roots) using the formula. Some, random, non integer roots.

", "licence": "Creative Commons Attribution 4.0 International"}, "statement": "

If we have a quadratic equation of the form  \\( ax^2 + bx +c = 0 \\),  we can use the Quadratic Formula:

\n

 

\n

\\( \\LARGE x= \\frac{-b \\pm \\sqrt{b^2 -4ac}}{2a} \\)

\n

 

\n

to find the roots of the equation. (Note the plus-or-minus means there are two solutions, not just one.)

\n

It is also sometimes known as Shreedhara Acharya's formula, named after the 10th century Indian mathematician who first derived it.

", "advice": "

We are asked to find the roots of various quadratic equations using the Quadratic Formula. To enable us to do this, we are first asked to identify the co-efficients  \\( a \\), \\( b \\) and \\( c \\) each time.

\n

\n

a)

\n

\\( \\simplify{ {a1}x^2 + {b1}x + {c1} } =0 \\)

\n

The co-efficients of this equation can simply be read from the equation, taking care to take account of positive and negative values:

\n

\\( a = \\)  \\( \\var{a1}\\)     \\( b = \\)  \\( \\var{b1}\\)   and  \\( c = \\)  \\( \\var{c1}\\)

\n

We now write the equation substituting these values in the correct places and, again, being careful with any negative values:

\n

\\( x= \\frac{-b \\pm \\sqrt{b^2 -4ac}}{2a} \\)     becomes     \\( x= \\frac{-(\\var{b1}) \\pm \\sqrt{(\\var{b1})^2 -4 \\times (\\var{a1}) \\times (\\var{c1})}}{2 \\times (\\var{a1})} \\)

\n

Simplify this as much as possible (mainly the expression inside the square root and the denominator):

\n

\\( x= \\frac{\\simplify{-{b1}} \\pm \\sqrt{\\simplify{{b1}^2 -4*{a1}*{c1}}}}{\\simplify{2{a1}}} \\)

\n

Now, carry out this calculation twice, first using the plus (\\( + \\))  and then using the minus (\\( - \\)).

\n

This will give you the two roots:    \\( x = \\var{x1} \\)  and   \\( x = \\var{x2} \\)

\n

 

\n

 

\n

b)

\n

\\( \\simplify{ {a2}x^2 + {b2}x + {c2} } =0 \\)

\n

The co-efficients of this equation can simply be read from the equation, taking care to take account of positive and negative values:

\n

\\( a = \\)  \\( \\var{a2}\\)     \\( b = \\)  \\( \\var{b2}\\)   and  \\( c = \\)  \\( \\var{c2}\\)

\n

We now write the equation substituting these values in the correct places and, again, being careful with any negative values:

\n

\\( x= \\frac{-b \\pm \\sqrt{b^2 -4ac}}{2a} \\)     becomes     \\( x= \\frac{-(\\var{b2}) \\pm \\sqrt{(\\var{b2})^2 -4 \\times (\\var{a2}) \\times (\\var{c2})}}{2 \\times (\\var{a2})} \\)

\n

Simplify this as much as possible (mainly the expression inside the square root and the denominator):

\n

\\( x= \\frac{\\simplify{-{b2}} \\pm \\sqrt{\\simplify{{b2}^2 -4*{a2}*{c2}}}}{\\simplify{2{a2}}} \\)

\n

Now, carry out this calculation twice, first using the plus (\\( + \\))  and then using the minus (\\( - \\)).

\n

This will give you the two roots:    \\( x = \\var{y1} \\)  and   \\( x = \\var{y2} \\)

\n

 

\n

 

\n

c)

\n

\\( \\simplify{ {a3}x^2 + {b3}x + {c3} } =0 \\)

\n

The co-efficients of this equation can simply be read from the equation, taking care to take account of positive and negative values:

\n

\\( a = \\)  \\( \\var{a3}\\)     \\( b = \\)  \\( \\var{b3}\\)   and  \\( c = \\)  \\( \\var{c3}\\)

\n

We now write the equation substituting these values in the correct places and, again, being careful with any negative values:

\n

\\( x= \\frac{-b \\pm \\sqrt{b^2 -4ac}}{2a} \\)     becomes     \\( x= \\frac{-(\\var{b3}) \\pm \\sqrt{(\\var{b3})^2 -4 \\times (\\var{a3}) \\times (\\var{c3})}}{2 \\times (\\var{a3})} \\)

\n

Simplify this as much as possible (mainly the expression inside the square root and the denominator):

\n

\\( x= \\frac{\\simplify{-{b3}} \\pm \\sqrt{\\simplify{{b3}^2 -4*{a3}*{c3}}}}{\\simplify{2{a3}}} \\)

\n

Now, carry out this calculation twice, first using the plus (\\( + \\))  and then using the minus (\\( - \\)).

\n

This will give you the two roots:    \\( x = \\var{z1} \\)  and   \\( x = \\var{z2} \\)

\n

\n

\n

\n

", "rulesets": {}, "builtin_constants": {"e": true, "pi,\u03c0": true, "i": true}, "constants": [], "variables": {"a1": {"name": "a1", "group": "Question A", "definition": "random(2..9)", "description": "", "templateType": "anything", "can_override": false}, "x1": {"name": "x1", "group": "Question A", "definition": "random(-9..9 #0.5 except 0 except 1 except {a1})", "description": "", "templateType": "anything", "can_override": false}, "x2": {"name": "x2", "group": "Question A", "definition": "random(-9..9 except 0 except 1 except {a1} except {x1})", "description": "", "templateType": "anything", "can_override": false}, "b1": {"name": "b1", "group": "Question A", "definition": "-{a1}*({x1}+{x2})", "description": "", "templateType": "anything", "can_override": false}, "c1": {"name": "c1", "group": "Question A", "definition": "{a1}*{x1}*{x2}", "description": "", "templateType": "anything", "can_override": false}, "a2": {"name": "a2", "group": "Question B", "definition": "random(2..9 except {a1})", "description": "", "templateType": "anything", "can_override": false}, "y1": {"name": "y1", "group": "Question B", "definition": "random(-9..9 #0.5 except 0 except 1 except {a2}) ", "description": "", "templateType": "anything", "can_override": false}, "y2": {"name": "y2", "group": "Question B", "definition": "random(-9..9 except 0 except 1 except {a2} except {y1})", "description": "", "templateType": "anything", "can_override": false}, "b2": {"name": "b2", "group": "Question B", "definition": "-{a2}*({y1}+{y2})", "description": "", "templateType": "anything", "can_override": false}, "c2": {"name": "c2", "group": "Question B", "definition": "{a2}*{y1}*{y2}", "description": "", "templateType": "anything", "can_override": false}, "a3": {"name": "a3", "group": "Question C", "definition": "random(2..9 except {a1} except {a2})", "description": "", "templateType": "anything", "can_override": false}, "z1": {"name": "z1", "group": "Question C", "definition": "random(-9..9 except 0 except 1 except {a3})", "description": "", "templateType": "anything", "can_override": false}, "z2": {"name": "z2", "group": "Question C", "definition": "random(-9..9 #0.5 except 0 except 1 except {a3} except {z1})", "description": "", "templateType": "anything", "can_override": false}, "b3": {"name": "b3", "group": "Question C", "definition": "-{a3}*({z1}+{z2})", "description": "", "templateType": "anything", "can_override": false}, "c3": {"name": "c3", "group": "Question C", "definition": "{a3}*{z1}*{z2}", "description": "", "templateType": "anything", "can_override": false}}, "variablesTest": {"condition": "", "maxRuns": 100}, "ungrouped_variables": [], "variable_groups": [{"name": "Question B", "variables": ["y1", "y2", "a2", "b2", "c2"]}, {"name": "Question C", "variables": ["z1", "z2", "a3", "b3", "c3"]}, {"name": "Question A", "variables": ["x1", "x2", "a1", "b1", "c1"]}], "functions": {}, "preamble": {"js": "", "css": ""}, "parts": [{"type": "information", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null}, {"type": "information", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "

For the following equations, first identify the co-efficients, then use the formula to calculate the roots:

"}, {"type": "gapfill", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": false, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "

\\( \\simplify{ {a1}x^2 + {b1}x + {c1} } =0 \\)

\n

The co-efficients of this equation are:

\n

\\( a = \\)  [[0]]   \\( b = \\)  [[1]]   and  \\( c = \\)  [[2]]

\n

 

\n

Now use the formula to find the roots:

\n

\\( x_1 = \\)  [[3]]

\n

\\( x_2 = \\)  [[4]]

\n

(If you are sure that your roots are correct but they are marked wrong, switch them around).

", "gaps": [{"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{a1}", "maxValue": "{a1}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{b1}", "maxValue": "{b1}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{c1}", "maxValue": "{c1}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{x1}", "maxValue": "{x1}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{x2}", "maxValue": "{x2}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}], "sortAnswers": false}, {"type": "gapfill", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": false, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "

\\( \\simplify{ {a2}x^2 + {b2}x + {c2} } =0 \\)

\n

The co-efficients of this equation are:

\n

\\( a = \\)  [[0]]   \\( b = \\)  [[1]]   and  \\( c = \\)  [[2]]

\n

 

\n

Now use the formula to find the roots:

\n

\\( x_1 = \\)  [[3]]

\n

\\( x_2 = \\)  [[4]]

\n

(If you are sure that your roots are correct but they are marked wrong, switch them around).

", "gaps": [{"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{a2}", "maxValue": "{a2}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{b2}", "maxValue": "{b2}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{c2}", "maxValue": "{c2}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{y1}", "maxValue": "{y1}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{y2}", "maxValue": "{y2}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}], "sortAnswers": false}, {"type": "gapfill", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": false, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "

\\( \\simplify{ {a3}x^2 + {b3}x + {c3} } =0 \\)

\n

The co-efficients of this equation are:

\n

\\( a = \\)  [[0]]   \\( b = \\)  [[1]]   and  \\( c = \\)  [[2]]

\n

 

\n

Now use the formula to find the roots:

\n

\\( x_1 = \\)  [[3]]

\n

\\( x_2 = \\)  [[4]]

\n

(If you are sure that your roots are correct but they are marked wrong, switch them around).

", "gaps": [{"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{a3}", "maxValue": "{a3}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{b3}", "maxValue": "{b3}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{c3}", "maxValue": "{c3}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{z1}", "maxValue": "{z1}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}, {"type": "numberentry", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "{z2}", "maxValue": "{z2}", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "showFractionHint": true, "notationStyles": ["plain", "en", "si-en"], "correctAnswerStyle": "plain"}], "sortAnswers": false}], "partsMode": "all", "maxMarks": 0, "objectives": [], "penalties": [], "objectiveVisibility": "always", "penaltyVisibility": "always"}]}], "allowPrinting": true, "navigation": {"allowregen": true, "reverse": true, "browse": true, "allowsteps": true, "showfrontpage": true, "showresultspage": "oncompletion", "navigatemode": "sequence", "onleave": {"action": "none", "message": ""}, "preventleave": true, "startpassword": ""}, "timing": {"allowPause": true, "timeout": {"action": "none", "message": ""}, "timedwarning": {"action": "none", "message": ""}}, "feedback": {"showactualmark": true, "showtotalmark": true, "showanswerstate": true, "allowrevealanswer": true, "advicethreshold": 0, "intro": "", "reviewshowscore": true, "reviewshowfeedback": true, "reviewshowexpectedanswer": true, "reviewshowadvice": true, "feedbackmessages": []}, "diagnostic": {"knowledge_graph": {"topics": [], "learning_objectives": []}, "script": "diagnosys", "customScript": ""}, "contributors": [{"name": "Michael Proudman", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/269/"}], "extensions": [], "custom_part_types": [], "resources": []}