10a(x-y)-5b(y-x)
问题描述：
10a(x-y)-5b(y-x)
(x-y)的平方
答
10a(x-y)-5b(y-x)
=10a(x-y)+5b(x-y)
=5(x-y)(2a+5b);
(x-y)^2
=x^2-2xy+y^2.