(3y-9)分之y-（y.y-y-6)分之5等于多少
问题描述：
(3y-9)分之y-（y.y-y-6)分之5等于多少
快哈~
答
y/(3y-9)-5/(y^2-y-6)
=y/3(y-3)-5/(y-3)(y+2)
=y(y+2)/3(y-3)(y+2)-15/(3(y-3)(y+2)
=y^2+2y-15/(3(y-3)(y+2)
=(y+5)(y-3)/(3(y-3)(y+2)
=(y+5)/3(y+2)