x²-y/ax-bx+ay-by=?
问题描述：
x²-y/ax-bx+ay-by=?
答
ax-bx+ay-by
=(ax+ay)-(bx+by)
=a(x+y)-b(x+y)
=(a-b)(x+y)
原式=（x+y）（x-y）/(a-b)(x+y)
=(x-y)/(a-b)