3x/(x-3)^2+x/x-3
=3x/(x-3)^2+x(x-3)/(x-3)^2
=[3x+x(x-3)]/(x-3)^2
=(3x+x^2-3x)/(x-3)^2
=x^2/(x-3)^2
=4/(-2-3)^2
=4/25为什么是x(x-3)/(x-3)^2不是x^2/(x-3)^2分子和分母同乘以(x-3)x/(x-3)=x(x-3)/(x-3)^2哦 谢了