代数式 初二

Question

急急急急 快一点

Answer 1

1/x-1/y=(y-x)/xy=3,x-y=-3xy
(5x-5y+xy)/(x-y-xy)=(-15xy+xy)/(-3xy-xy)=-14xy/(-4xy)=7/2
分数给我吧？嘿嘿！

Answer 2

1/x-1/y=3
(y-x)/xy=3
y-x=3xy
x-y=-3xy

（5x+xy-5y)/(x-xy-y)
=[5(x-y)+xy]/[(x-y)-xy]
=(-15xy+xy)/(-3xy-xy)
=-14xy/(-4xy)
=7/2

参考资料：http://zhidao.baidu.com/question/111244963.html

Answer 3

7/2
已知的式子左右同乘xy的y-x=3xy
带入下式得结果