(x-y)7÷(y-x)4+(-x-y)8÷(x+y)5.

问题描述:

(x-y)7÷(y-x)4+(-x-y)8÷(x+y)5

原式=(x-y)7÷(x-y)4+(x+y)8÷(x+y)5
=(x-y)3+(x+y)3
=x3-3x2y+3xy2-y3+x3+3x2y+3xy2+y3
=2x3+6xy2