7.1 Integration By Parts/53

$y=xe^{-0.4x}~~~x=0,x=1$

Failed to parse (syntax error): {\displaystyle \underbrace{\int_{0}^{5}xe^{-0.4x}dx}_ { }

${\begin{aligned}{\begin{aligned}u&=x\quad dv=e^{-0.4x}dx\\[0.6ex]du&=dx\qquad v={\frac {5}{2}}e^{-0.4x}\end{aligned}}\\[2ex]\end{aligned}}$

$\left[{\frac {5}{2}}e^{-0.4x}\right]+\int _{5}^{0}{\frac {5}{2}}e^{-0.4x}dx$