Question

(-x+y)(y²+x²)再乘以( )就等于x`4-y`4 A.X-Y B.X+Y C.-X+Y D

Answer 1

就相当于用x^4-y^4除以(-x+y)(y^2+x^2)得到的结果,就是所求.

(x^4-y^4)/[(-x+y)(y^2+x^2)]

=[(x^2-y^2)(x^2+y^2)]/[(y-x)(y^2+x^2)]

=(x^2-y^2)/(y-x)

=(x+y)(x-y)/(y-x)

=-(x+y)(y-x)/(y-x)

=-(x+y)

——答案：D