g(x)=(x-2m)^3-2(x-2m)+2n
证明:f(x)+g(2m-x)
= x^3-2x+(2m-x-2m)^3-2(2m-x-2m)+2n
=x^3-2x-x^3+2x+2n
=2n
所以f(x)与g(x)图像关于A(m,n)对称