{x+y=450,60%y-40%x=30

x+y=450;40%x+30=60%y {x+y=450,60%y-40%x=30 x+y/3+x-y/2=6 4(x+y)-2(x-y)=40 （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 推倒公式:(x+y)(x*x-3x+y*y)=x*x*x+y*y*y怎么做. x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 X+Y=40,(X*Y)/(X+Y)=7.5 (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+3y)(x+4y)=-40y的值为根号11 (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) 化简 x / y(x+y) - y / x(x+y) = 化简 x-y/(y-x)^3= (x+y)(2x-3y)=? x(x+y)(x-y)-y(y+x)(y-x)=(x-y)( )填空 x+x+x+y=60 .x-y=4 y(x+y)+(x-y)²-（x+y）（x-y）,其中x=-1/3,y=3