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This question concerns ratios of algebraic expressions.
\nBy this we mean expressions of the form $\\displaystyle \\frac{p(x)}{q(x)}$ where $p(x)$ and $q(x)$ are algebraic expressions.
\nIf you want to input such an expression into the system you HAVE TO BE CAREFUL AND USE BRACKETS or mistakes will occur.
\nOnce again, the preview answer box displaying your input in mathematical notation beside the input boxes in parts a, b and c is very useful as it shows what the system thinks you have entered.
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", "licence": "Creative Commons Attribution 4.0 International"}, "rulesets": {"std": ["all", "!collectNumbers"]}, "parts": [{"showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacementStrategy": "originalfirst", "prompt": "Suppose we wanted to input the expression $\\displaystyle \\frac{\\var{a}+\\var{b}x}{\\var{c}+\\var{d}y}$ into the system.
\nWhich of the following input expressions are incorrect?
\n[[0]]
\nChoose the incorrect input(s).
\nAfter you have clicked Submit part, click on Show Feedback and you will be given more detail on your choices.
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{a}+{b}x/({c}+{d}y)
{a}+{b}x/{c}+{d}y
({a}+{b}x)/{c}+{d}y
({a}+{b}x)/({c}+{d}y)
{a}+{b}x/({c}+{d}y)
{a}+{b}x/{c}+{d}y
({a}+{b}x)/{c}+{d}y
Input the expression $\\displaystyle \\frac{\\var{b}+\\var{a}y}{\\var{d}+\\var{c}z}$. [[0]]
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", "scripts": {}, "customName": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "type": "gapfill", "useCustomName": false, "variableReplacements": [], "customMarkingAlgorithm": "", "gaps": [{"type": "jme", "checkingAccuracy": 0.0001, "showFeedbackIcon": true, "checkingType": "absdiff", "failureRate": 1, "unitTests": [], "scripts": {}, "checkVariableNames": false, "variableReplacements": [], "customMarkingAlgorithm": "", "marks": "2.5", "showCorrectAnswer": true, "answerSimplification": "std", "valuegenerators": [{"name": "x", "value": ""}, {"name": "y", "value": ""}], "variableReplacementStrategy": "originalfirst", "vsetRangePoints": 5, "answer": "({a} -(({b} * x + {c}) * e ^ (( -{2}) * x))) / ((x + {2 b}) * (y -{3* d}))", "extendBaseMarkingAlgorithm": true, "customName": "", "useCustomName": false, "vsetRange": [0, 1], "showPreview": true}], "sortAnswers": false, "marks": 0}], "variablesTest": {"condition": "", "maxRuns": 100}, "tags": [], "functions": {}, "advice": "The correct input is ({a}+{b}x)/({c}+{d}y)
- the rest are incorrect and you should have chosen those.
A correct input is ({b} + {a}y) / ({c} + {d}z)
. Also correct is ({a}y+{b}) / ({c} + {d}z)
etc.
A correct input is ({d}z + {b}) / ((x + {a})*(y + {c}))
.
Note the denominator (the bottom of the ratio) has to have two brackets, i.e. ((x + {a})*(y + {c}))
as otherwise the expression ({d}z + {b}) / (x + {a})*(y + {c})
is seen by the system as $\\displaystyle \\left(\\simplify[std]{({d} * z + {b}) / (x + {a})}\\right) (y + \\var{c})$
A correct input is ({a} -({b}x + {c})*e ^ ( -{2}x)) / ((x + {2*b})*(y -{3*d}))
.