第1997题:分部积分法
求 ∫x3exdx\int x^3 \mathrm{e}^x dx∫x3exdx .
A. ex(2x3−3x2+12x−12)\mathrm{e}^x (2x^3-3x^2+12x-12)ex(2x3−3x2+12x−12) +C +C+C
B. ex(x3−3x2+6x−6)\mathrm{e}^x (x^3-3x^2+6x-6)ex(x3−3x2+6x−6) +C+C+C
C. ex(x−1)3\mathrm{e}^x (x-1)^3ex(x−1)3 +C +C+C
D.ex(x−2)3 \mathrm{e}^x (x-2)^3ex(x−2)3 +C+C+C
分部积分法在之前的英语题中用到,其公式由 (uv)′=u′v+uv′(uv)'=u'v+uv'(uv)′=u′v+uv′ 推导而来:∫udv=uv−∫vdu\int u dv=uv-\int v du∫udv=uv−∫vdu .