计算3y/(2x+2y)+2xy/x^2+xy
问题描述：
计算3y/(2x+2y)+2xy/x^2+xy
答
3y/(2x+2y)+2xy/(x^2+xy)
=3y/[2(x+y)] + 2y/(x+y)]
=(3y+4y)/[2(x+y)]
=7y/[2(x+y)]