Mathematics

Mathematics

Problem

Let I=∫x4ex dxI=\displaystyle \int x^{4} e^{x}\,dx. (a) Obtain the value of II. (b) Differentiate your answer with respect to xx to verify that it yields x4exx^{4} e^{x}.
Intuitive explanation

This problem is about integration by parts, a technique for handling products of polynomials and exponentials. The key insight is that you'll need to apply the integration-by-parts formula repeatedly—each time you integrate, the polynomial power drops by one, until you're left with just exe^x. Part (b) then gives you a built-in check: differentiation should undo your work and return you to the original integrand, which is a powerful way to catch errors.

Intuitive explanation

This problem is about integration by parts, a technique for handling products of polynomials and exponentials. The key insight is that you'll need to apply the integration-by-parts formula repeatedly—each time you integrate, the polynomial power drops by one, until you're left with just exe^x. Part (b) then gives you a built-in check: differentiation should undo your work and return you to the original integrand, which is a powerful way to catch errors.

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