{ 1/x+1/y=1/2

1、x(x-y)(x+y)-x(x+y)^2 先化简再求值(x-y)(x+y)-(x-2y) 的完全平方+x(3x-5y)-(x-y)(x-2y),其中x=1/2 y (3x-y)^2+(3x+y)(3x-y),x=1,y=-2 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 已知4x=9y求(1)x+y/y (2)y-x/2x (1)(x^2/x)-y-x-y y=(x^2+x)/(x+1) 2(x+y) 3x+3y=24 x+y/2x x y/2y= 1 设x>1,y>0,若x^y+x^-y=2根号2,则x^y-x^-y等于 [(-x-y)(-x+y)-(x+y)^2-x(y-y^2)}÷1/2y 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 x+y=1,xy=-1/2,求x(x+y)(x-y)-x(x+y)2