A maths problem

晉文公

BobbyRobson

d咗之後加個2n(x^2 +1)^n-1
再減個2n(x^2 +1)^n-1
搞掂.
有錯請指.

Saha

the expression=x*d(x^2+1)^n/dn+(x^2+1)^n
=x*n*(x^2+1)^(n-1)*2x+(x^2+1)^n
=(2n+1)(x^2+1)^n-2n(x^2+1)^n+2x^2n(x^2+1)^(n-1)
=(2n+1)(x^2+1)^N-(2x^2n+2n-2x^2n)(X^2+1)^(n-1)
=(2n+1)(x^2+1)^N-2n*(X^2+1)^(n-1)

晉文公

Actually I hv finished by myself

But THANKS Saha and Robson