y=-1/2*x^2+x

1、x(x-y)(x+y)-x(x+y)^2 y=(x^2+x)/(x+1) 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 (1)(x^2/x)-y-x-y (3x-y)^2+(3x+y)(3x-y),x=1,y=-2 已知4x=9y求(1)x+y/y (2)y-x/2x {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 函数,y=3x/(x^2+x+1) ,x 函数y=3x/(x^2+x+1) （x x+y=1,xy=-1/2,求x(x+y)(x-y)-x(x+y)2 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