(x^2-1)拆开为x(x-1/x),(x-1/x)挪到最前面(x+1/x)(x^2+1/x^2)(x^4+1/x^4)...(x^16+1/x^16)(x^2-1)=(x-1/x)(x+1/x)(x^2+1/x^2)(x^4+1/x^4)...(x^16+1/x^16)x=(x^2-1/x^2)(x^2+1/x^2)(x^4+1/x^4)...(x^16+1/x^16)x=.=(...