(1)1200+4y=500x (2)2400+20x=20y 求x,

(1)1200+4y=500x (2)2400+20x=20y 求x, {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 （1）1200+4Y=500X(2) 2400+20X=20Y求X和Y x+y+2(-x-y+1)=3(1-y-x)-4-(y+x-1),x+y=? 先化简 再求值 (2x-y)(y+x)-(x-2y)(2y+x)-(-3y+x)^2其(√x+1)+y^2+4=-4y 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 已知:【(x²+y²)-(x-y)²+2y(x-y)】/4y=1,求4x/4x²-y²-1/2x+y 已知x-y=1,求[(x+2y)^2+(2x+y)(x-4y)-3(x+y)(x-y)]除以y的值大神们帮帮忙 已知x-y=1,求[(x+2y)²+(2x+y)(x-4y)-3(x+y)(x-y)]÷y的值 [(y-2x)(-2x-y)-4(x-2y)²]*2y,其中x=1,y=2 [(y-2x)(-2x-y)+4(x-2y)平方]/3y,其中x=1,y=-3 [(x+y)(x-y)-(x-y)^2-4xy]/2y,其中x=1,y=-1 [(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 先化简,再求值:[(x＋y)(x-y)-(x-y)²+2y(x+y)]除4y,其中x=2,y=1 [(2x-y)^2-y(y-4x)-8x]其中x=-1/2 9y=3x-(x-1),4(x+y)-(2x+4)=8y 先化简,再求值(x-y/x+y)^2÷(y-x/x^2+2xy+y^2)^2*1/x+y,其中x=-4,y=1