// Numbas version: exam_results_page_options {"name": "Integration: Indefinite integral with 1/ (ax+b)^n", "extensions": [], "custom_part_types": [], "resources": [], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "question_groups": [{"pickingStrategy": "all-ordered", "questions": [{"preamble": {"js": "", "css": ""}, "metadata": {"notes": "\n\t\t

2/08/2012:

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Added tags.

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Added description.

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Added decimal point to forbidden strings along with message to user re input of numbers.

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Added a Step and message about Show steps included - losing 1 mark if used as it gives the formula for finding the integral. Increased marks to 3 for the question, so that can cope with losing a mark for using Show steps.

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Changed accuracy setting to relative difference of 0.00001 as we have negative powers.

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Checked calculation. OK.

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Added message in prompt  about including the constant of integration.

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Noted issue with steps-answer order and the messages/marks generated.

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Changed numerator to the range 2..5.

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Improved display in Advice.

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\n\t\t", "licence": "Creative Commons Attribution 4.0 International", "description": "

Find $\\displaystyle \\int \\frac{a}{(bx+c)^n}\\;dx$

"}, "name": "Integration: Indefinite integral with 1/ (ax+b)^n", "showQuestionGroupNames": false, "parts": [{"stepsPenalty": 1, "scripts": {}, "marks": 0, "showCorrectAnswer": true, "prompt": "\n\t\t\t

$\\displaystyle \\int \\simplify[std]{{b}/(({a}*x+{d})^{n})} dx= \\phantom{{}}$[[0]]

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Input all numbers as integers or fractions and not decimals. Remember to include the constant of integration $C$.

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Click on Show steps to get help. You will lose 1 mark by doing so.

\n\t\t\t", "gaps": [{"checkingtype": "reldiff", "notallowed": {"message": "

Input all numbers as integers or fractions and not decimals.

", "strings": ["."], "partialCredit": 0, "showStrings": false}, "vsetrangepoints": 5, "checkvariablenames": false, "answer": "(-{b})/({a*(n-1)}*({a}*x+{d})^{n-1}) + C", "showCorrectAnswer": true, "expectedvariablenames": [], "type": "jme", "scripts": {}, "marks": 3, "checkingaccuracy": 0.0001, "showpreview": true, "answersimplification": "std", "vsetrange": [0, 1]}], "steps": [{"showCorrectAnswer": true, "prompt": "

 \\[\\int (ax+b)^n \\;dx = \\frac{1}{a(n+1)}(ax+b)^{n+1}+C\\]

", "marks": 0, "scripts": {}, "type": "information"}], "type": "gapfill"}], "functions": {}, "advice": "\n\t

Let $y = \\simplify[std]{{a}*x+{d}}$. Then,
\\[\\simplify[std]{{b}/(({a}*x+{d})^{n})} = \\simplify[std]{{b}/(y^{n})}.\\]

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Now,
\\[\\int \\simplify[std]{{b}/({a}*x+{d})^{n}} dx = \\int \\simplify[std]{{b}/(y^{n})} \\frac{dx}{dy} dy.\\]

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Rearrange $y = \\simplify[std]{{a}x+{d}}$ to get $\\displaystyle x = \\simplify[std]{(y-{b})/{a}}$, and hence $\\displaystyle\\frac{dx}{dy} = \\frac{1}{\\var{a}}$.

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$\\displaystyle \\int \\frac{1}{y^n} dx = -\\frac{1}{(n-1)y^{n-1}} + C$ is a standard integral, so we can now calculate the desired integral:

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\\[\\int \\simplify[std]{{b}/(y^{n})} \\frac{dx}{dy} dy = \\simplify[std]{{b}/({n-1}*y^{n-1})} \\cdot \\frac{1}{\\var{a}} + C = \\simplify[std]{(-{b})/({a*(n-1)}*({a}*x+{d})^{n-1}) + C}.\\]

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Find the following indefinite integral.

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Input the constant of integration as $C$.

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