// Numbas version: exam_results_page_options {"name": "Vectors: Linear Combinations 1", "extensions": [], "custom_part_types": [], "resources": [], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "question_groups": [{"pickingStrategy": "all-ordered", "questions": [{"name": "Vectors: Linear Combinations 1", "tags": [], "metadata": {"description": "

Given 3 vectors $\\mathbf v$, $\\mathbf a$ and $\\mathbf b$, find the constants $c_1$ and $c_2$ such that $\\mathbf v = c_1 \\mathbf a + c_2 \\mathbf b$ .

", "licence": "Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International"}, "statement": "

Find the values of the constants $c_1$ and $c_2$ such that the vector $\\mathbf v = \\var{v}$ is a linear combination of the vectors $\\mathbf a=\\var{a}$ and $\\mathbf b=\\var{b}$: \\[ \\mathbf v = c_1 \\mathbf a + c_2 \\mathbf b. \\]

", "advice": "

We are trying to find the constants $c_1$ and $c_2$ such that we can express $\\mathbf v$ as a linear combination of the vectors $\\mathbf a$ and $\\mathbf b$:

\n

\\[ \\var{v} = c_1 \\var{a} + c_2 \\var{b} ,\\]

\n

\n

We can calculate $c_1$ and $c_2$ by solving the simultaneous equations

\n

\\[ \\begin{split} \\var{v[0]} &\\,= \\simplify[all,!noLeadingMinus]{{a[0]}c_1 + {b[0]} c_2}  \\\\ \\var{v[1]} &\\,= \\simplify[all,!noLeadingMinus]{{a[1]}c_1 + {b[1]} c_2} . \\end{split} \\]

\n

\n

We find $c_1 = \\var{c1}$ and $c_2 = \\var{c2}$, and therefore,

\n

\\[\\var{v} = \\simplify[all,!noLeadingMinus]{{c1}{a}+{c2}{b}}. \\]

\n

", "rulesets": {}, "extensions": [], "builtin_constants": {"e": true, "pi,\u03c0": true, "i": true}, "constants": [], "variables": {"a": {"name": "a", "group": "Ungrouped variables", "definition": "vector(repeat(random(-5..5 except 0),2))", "description": "", "templateType": "anything", "can_override": false}, "b": {"name": "b", "group": "Ungrouped variables", "definition": "vector(random(-5..-1),random(-5..5))", "description": "", "templateType": "anything", "can_override": false}, "v": {"name": "v", "group": "Ungrouped variables", "definition": "c1*a+c2*b", "description": "", "templateType": "anything", "can_override": false}, "c1": {"name": "c1", "group": "Ungrouped variables", "definition": "random(-4..5 except 0)", "description": "", "templateType": "anything", "can_override": false}, "c2": {"name": "c2", "group": "Ungrouped variables", "definition": "random(-5..6 except [0,c1])", "description": "", "templateType": "anything", "can_override": false}}, "variablesTest": {"condition": "", "maxRuns": 100}, "ungrouped_variables": ["a", "b", "v", "c1", "c2"], "variable_groups": [], "functions": {}, "preamble": {"js": "", "css": ""}, "parts": [{"type": "gapfill", "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": "

$c_1= $[[0]]

\n

$c_2= $[[1]]

", "gaps": [{"type": "jme", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "answer": "{c1}", "showPreview": true, "checkingType": "absdiff", "checkingAccuracy": 0.001, "failureRate": 1, "vsetRangePoints": 5, "vsetRange": [0, 1], "checkVariableNames": false, "singleLetterVariables": false, "allowUnknownFunctions": true, "implicitFunctionComposition": false, "caseSensitive": false, "valuegenerators": []}, {"type": "jme", "useCustomName": false, "customName": "", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "answer": "{c2}", "showPreview": true, "checkingType": "absdiff", "checkingAccuracy": 0.001, "failureRate": 1, "vsetRangePoints": 5, "vsetRange": [0, 1], "checkVariableNames": false, "singleLetterVariables": false, "allowUnknownFunctions": true, "implicitFunctionComposition": false, "caseSensitive": false, "valuegenerators": []}], "sortAnswers": false}], "partsMode": "all", "maxMarks": 0, "objectives": [], "penalties": [], "objectiveVisibility": "always", "penaltyVisibility": "always", "contributors": [{"name": "Ben McGovern", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/4872/"}]}]}], "contributors": [{"name": "Ben McGovern", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/4872/"}]}