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MTH 102 MTH 102 Past Questions Objective Question

Question

Simplify ∫ 3x2ex3 dx.
Options
A <i>e<sup>x<sup>2</sup></sup> + C</i>
B <i>e<sup>x<sup>3</sup></sup> + C</i>
Correct Answer
C <i>e<sup>x<sup>4</sup></sup> + C</i>
D <i>e<sup>x<sup>5</sup></sup> + C</i>
Correct Answer

Option B is the correct answer.

Detailed Explanation

This integral can be solved using substitution.Let u = x3.Then, differentiate u with respect to x to find du:du/dx = 3x2, so du = 3x2 dx.Substitute u and du into the integral:∫ eu duThe integral of eu with respect to u is eu + C.Now, substitute u = x3 back into the result:ex3 + C.This matches option B.

Hint

Look for a part of the integrand whose derivative is also present (or a constant multiple of it). In this case, if you let u = x3, its derivative 3x2 is right there!

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