晉文公 發表於 2004-10-24 16:11:01

A maths problem

:o :o:o:o :o

BobbyRobson 發表於 2004-10-24 17:31:29

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 發表於 2004-10-24 17:33:05

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 發表於 2004-10-24 17:54:34

Actually I hv finished by myself

But THANKS Saha and Robson :D
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