凑微分法2x/1+x^2dx怎么等于1/1+x^2dx^2

Question

凑微分法2x/1+x^2dx 怎么等于1/1+x^2dx^2

Answer 1

dx^2,表示对x^2求导得2x, 2x/1+x^2dx 式中2x放回到dx^2积分的,还可以进一步
1/1+x^2dx^2=1/1+x^2d(x^2+1)=ln(x^2+1)