（2m-n)ˆ(2m+n)ˆ2(nˆ2+4mˆ2)ˆ2（x+y)ˆ2(x-y)ˆ2-(x-y)(x+y)(xˆ2+yˆ2)

（2m-n)ˆ(2m+n)ˆ2(nˆ2+4mˆ2)ˆ2（x+y)ˆ2(x-y)ˆ2-(x-y)(x+y)(xˆ2+yˆ2)
（2m-n)ˆ(2m+n)ˆ2(nˆ2+4mˆ2)ˆ2
（x+y)ˆ2(x-y)ˆ2-(x-y)(x+y)(xˆ2+yˆ2)

（2m-n)ˆ(2m+n)ˆ2(nˆ2+4mˆ2)ˆ2（x+y)ˆ2(x-y)ˆ2-(x-y)(x+y)(xˆ2+yˆ2)
第一道全是幂的形式么、没看懂
第二道=(x+y)(x-y)(x+y)(x-y)-(x^2-y^2)(x^2+y^2)=(x^2-y^2)(x^2-y^2)-(x^2-y^2)(x^2+y^2)=(x^2-y^2)(x^2-y^2-x^2-y^2)=-2y^2(x^2-y^2)