已知1/x-1/y=5 求分式-x+xy+y/2x+7xy-2y

问题描述:

已知1/x-1/y=5 求分式-x+xy+y/2x+7xy-2y

将1/x-1/y=5通分,得y-x/xy=5,
两边同时乘以xy,得y-x=5xy,
带入-x+xy+y/2x+7xy-2y,得5xy+xy/-2*5xy+7xy,
合并同类项,得6xy/-3xy=-2
即,原式等于-2