x+x+x+y=42 x+y+y+y=30 求x=( )y=( )

x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 化简 x / y(x+y) - y / x(x+y) = （x+y-5)*（x+y-5)+（x-y+3)=0 x*x-y*y 已知:3x-5y=0,求x/y,x-y/y,x-y/x x(x+y)(x-y)-y(y+x)(y-x)=(x-y)( )填空 推倒公式:(x+y)(x*x-3x+y*y)=x*x*x+y*y*y怎么做. (x+y)(x-y)+(x-y)平方-(x-y)(3x-y) 其中x=-2 y=3分之一 (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) x+x+y+y+y=21 ,x+x+y+y+y+y+y=27 ,x ,y=? x+x+y+y+y=21 ,x+x+y+y+y+y+y=27 ,x ,y=? y=x(x 化简 x-y/(y-x)^3= (x+y)(2x-3y)=? x+x+x+x+y+y+y=56 y(x+y)+(x-y)²-（x+y）（x-y）,其中x=-1/3,y=3 已知3x =2y 求x/x+y+y/x-y-y²/x²-y² 【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2=