可以这样想啊1/(x+x^3)=（x^2+1）/(x+x^3)-x^2/(x+x^3)=1/x-x/(x^2+1)∫1/(x+x^3)dx=Inx-1/2∫1/(x^2+1)d(x^2+1)=Inx-1/2In(x^2+1)取[1,2]时,原式＝In2-In1-1/2(In5-In2)=3/2In2-1/2In5传热传质系研究生为你解答,供...