x^2*x^2n*y^2n=x^2*(xy)^2n=(-4)^2*(-4*1/4)^2n=16*(-1)^2n=16*1=16不好意思，题打错了...是2n+1...不是2n..x^2*x^2n*y^2n=x^2(xy)^(2n+1)=(-4)^2(-4*1/4)^2n+1=16*(-1)^2n+1=16*-1=-16