已知x分之1+y分之1=5,x-2xy-y分之2x+5xy-2y的值是

显示全部楼层 · 2011-3-24 20:39:25

原式=2+7xy/(x-2xy-y)后面那个式子分子分母倒一下就是倒数(x-2xy-y)/7xy=1/7y-2/7-1/7x你的条件应该是x分之1-y分之1=5不然没法做(x-2xy-y)/7xy=1/7y-2/7-1/7x=-2/7-5/7=-1-1的倒数还是-1所以7xy/(x-2xy-y)=-1原式=2-1=1打了那么多字总该给点分吧

千问 · 2011-3-24 20:39:25

条件不足啊，是不是有什么条件没写啊？不过楼上是错的， “原式=2+7xy/(x-2xy-y)”应该是原式=2+9xy/(x-2xy-y)如果是x分之1-y分之1=5那么结果是5/7

千问 · 2011-3-24 20:39:25

已知x分之1+y分之1=5,则分式x+2xy+y分之2x-3xy+2y的值为？解：x，y均不为01/x + 1/y = 5(x+y)/x*y = 5x+y = 5*x*yx+2xy+y = x+y + 2xy = 5xy+2xy = 7xy2x-3xy+2y = 10xy-3xy = 7xy(2x-3xy+2y)/(x+2xy+y