查人人中国名人网汽车机油检测:help~~~~ =_=
来源：百度文库 编辑：查人人中国名人网 时间：2024/05/09 20:01:34
1/x - 1/y = 4
(2x + 3xy - 2y) / (x - 2xy - y) = ???
(2x + 3xy - 2y) / (x - 2xy - y) = ???
1/x - 1/y = 4
通分：(y-x)/xy=4,即y-x=4xy(1)
(2x + 3xy - 2y) / (x - 2xy - y)
=[3xy-2(y-x)]/[-2xy-(y-x)]
代入(1),用(y-x)表示xy,得
原式=(3xy-8xy)/(-2xy-4xy)
=-5/-6
=5/6
等式上下同时除以xy，得[2*(1/x)+3-2*(1/y)]/[(1/x)-2-(1/y)]
=[2*(1/x - 1/y)+3]/[(1/x - 1/y)-2]
=(2*4+3)/(4-2)
=11/2