x的4次幂-y的4次幂=(x²+y²)(x²-y²)=(x²+y²)(x+y)(x-y)4(x+y)²-(y-x)²=(2x+2y+y-x)(2x+2y-y+x)=(x+3y)(3x+y)
x的4次幂-y的4次幂=(x^2-y^2)(x^2+y^2)=(x-y)(x+y)(x^2+y^2) 4(x+y)²-(y-x)²=(2x+2y-y+x)(2x+2y+y-x)=(3x+y)(x+3y) 二者相等?