(x-2+1/x)^n(1) x>0(x-2+1/x)^n=(√x-1/√x)^2n 常数项为 中间项 C(2n,n) (2)x<0(x-2+1/x)^n=-(√-x-1/√-x)^2n 常数项为 中间项 -C(2n,n)
