(1)y=x,y+4x=15; (2)x+2x-3y=1; (3)x-7y=0,x-9y=8=0.

x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 2（x+y)-3(x-y)=3 ,4(x+y)+3(x-y)=15 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 x+y+2(-x-y+1)=3(1-y-x)-4-(y+x-1),x+y=? (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= x-2y=15,xy=-25,求x*x+4y*y-1 (x-4y)(2x+y)= 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 先化简 再求值 (2x-y)(y+x)-(x-2y)(2y+x)-(-3y+x)^2其(√x+1)+y^2+4=-4y 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 9y=3x-(x-1),4(x+y)-(2x+4)=8y [(2x-y)^2-y(y-4x)-8x]其中x=-1/2 1.(x-2y)(x+2y)-(x平方+y)(x平方-y) 2.(2x-y)(y+2x)-(2y+x)(2y-x)3.已知：x+y=6,x平方-y平方=48,求x,y的值4.x平方-2x分之x+2 -- x平方-4x+4分之x-1 4x(x-y)-(2x-3y)(2x-3y) x=1 y=-1 [(2x+y)²-y(y+4x)-8x】/4x,其中x=-1,y=2005 急 [(y-2x)(-2x-y)-4(x-2y)²]*2y,其中x=1,y=2