lim=x^3/e^x在x趋于无穷时=0.y'=e^x+xe^x,y''=e^x+e^x+xe^x,y''(0)=2.
j(t^2+2t+1)(t+1)/t^2dt= j (t^3+3t^2+3t+1)/t^2dt=jt^3+3t^2/t^2dt +j(3t+1)/t^2dt=jt+3dt+j(3t+1)//t^2dt=1/2t^2+3t+ j2t/t^2 dt+j(t+1)d/t^2=...j1/t^2dt^2+1/2j(2t+2)/t^2dt=...lnt^2+1/2j1/t^2dt^2+1/2j2/t^2dt=
1/t^2+3t+3/2lnt^2-1/t+c.
