(1)y=1/3x^2+3,y=1/3x^2-2; (2)y=-1/4(x+2)^2,y=-1/4(x-1)^2; (3

{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=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 已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-( (3x-y)^2+(3x+y)(3x-y),x=1,y=-2 [(2x+y)^2+(y+2x)(y-2x)-2y(4x-y)]/4y,其中x=1/2,y=1/3 先化简,再求值：[(x+y)(x-y)-(x-y)^2+2y(x-3y)]/(-4y),其中x=1,y=-2 9y=3x-(x-1),4(x+y)-(2x+4)=8y 若x=-1/4,能否确定代数式(2x-y)(2x+y)+(2x-y)(y-4x)+2y(y-3x)的值? 2(x+y) 3x+3y=24 x+y/2x x y/2y= 1 3x-2y=1 4x-5y (x+y)/2-(3x-y)/4=1