已知1/x+1/y=3 求3x+xy+3y/x-xy=y的值

来源：学生作业学帮网编辑：学帮网时间：2024/05/20 03:06:24

是求(3x+xy+3y)/(x-xy+y)吧?
(3x+xy+3y)/(x-xy+y) 上下同除以xy
=(3/y+1+3/x） / (1/y-1+1/x)
=[3(1/x+1/y)+1] / (1/x+1/y -1)
=(3×3+1)/(3-1)
=10/2
=5