assignment submission\nfor this assignment, you submit answers by question parts. the number \nassignment…

assignment submission\nfor this assignment, you submit answers by question parts. the number \nassignment scoring\nyour best submission for each question part is used for your score.\n8. -/2.08 points\nevaluate the integral.\n int_{0}^{1} (x^{2}+4)e^{-x}dx

assignment submission\nfor this assignment, you submit answers by question parts. the number \nassignment scoring\nyour best submission for each question part is used for your score.\n8. -/2.08 points\nevaluate the integral.\n int_{0}^{1} (x^{2}+4)e^{-x}dx

Answer

Explanation:

Step1: Use integration - by - parts formula $\int_{a}^{b}u\mathrm{d}v=uv|{a}^{b}-\int{a}^{b}v\mathrm{d}u$

Let $u = x^{2}+4$, $\mathrm{d}v=e^{-x}\mathrm{d}x$. Then $\mathrm{d}u = 2x\mathrm{d}x$, $v=-e^{-x}$. [ \begin{align*} \int_{0}^{1}(x^{2}+4)e^{-x}\mathrm{d}x&=-(x^{2}+4)e^{-x}\big|{0}^{1}+\int{0}^{1}2xe^{-x}\mathrm{d}x\ &=-(1 + 4)e^{-1}+(0 + 4)e^{0}+2\int_{0}^{1}xe^{-x}\mathrm{d}x\ &=- \frac{5}{e}+4+2\int_{0}^{1}xe^{-x}\mathrm{d}x \end{align*} ]

Step2: Apply integration - by - parts again on $\int_{0}^{1}xe^{-x}\mathrm{d}x$

Let $u = x$, $\mathrm{d}v=e^{-x}\mathrm{d}x$. Then $\mathrm{d}u=\mathrm{d}x$, $v=-e^{-x}$. [ \begin{align*} \int_{0}^{1}xe^{-x}\mathrm{d}x&=-xe^{-x}\big|{0}^{1}+\int{0}^{1}e^{-x}\mathrm{d}x\ &=-e^{-1}+0-\left(e^{-x}\big|_{0}^{1}\right)\ &=-\frac{1}{e}-(e^{-1}-e^{0})\ &=-\frac{1}{e}-\frac{1}{e}+1\ &=1-\frac{2}{e} \end{align*} ]

Step3: Substitute the result of $\int_{0}^{1}xe^{-x}\mathrm{d}x$ back

[ \begin{align*} \int_{0}^{1}(x^{2}+4)e^{-x}\mathrm{d}x&=-\frac{5}{e}+4+2\left(1-\frac{2}{e}\right)\ &=-\frac{5}{e}+4 + 2-\frac{4}{e}\ &=6-\frac{9}{e} \end{align*} ]

Answer:

$6-\frac{9}{e}$