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