{x+y=1000① 20x+30y=26000②

x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 1=x+y 2=20x+30y x+y/2+x-y/3=6,4(x+y)-3(x-y)=-20 {(x+y)/2+(x-y)/3=6 4(x+y)-3(x-y)=-20 4(x+y)-3(x-y)=-20,2/x+y+3/x-y=6 3（x+y)+2(x-3y)=20,30%x+60%y=10%*60 |x|+|y|=30 2|x|-3|y|=20 求x,y 填空：x-y/x+y=( )/x^2-y^2 （x-y)2•(y-x)³(x-y)=? y+y'-2y=2x 微分方程y - 2y' + y = x (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) 化简 x / y(x+y) - y / x(x+y) = (x-4y)(2x+y)= (x+y)(2x-3y)=? x+y>=2,x-y