1、令t=x-4 dt/dx=1则y=1/ty^(5)=(-1)^5*5!/t^6=-120/t^6=-120/(x-4)^62、y=1/(x+1)(x+2)=1/(x+1)-1/(x+2)则y^(n)=(-1)^n*n![1/(x+1)^n-1/(x+2)^n]
