(x-y)^2 = (x+y)^2 - 4xy为什么是这样算的

x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 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-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= (x+y)(x-y)+(x-y)平方-(x-y)(3x-y) 其中x=-2 y=3分之一 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 化简y(x+y)+(x+y)(x-y)-x^2 (x-4y)(2x+y)= (x+y)(2x-3y)=? x+y>=2,x-y x+y>=2,x-y y'-2y=(e^x)-x y'+2y/x=x通解 dy/dx=(2x*x*x*y-y*y*y*y)/(x*x*x*x-2x*y*y*y) x²-(x-2y)(x+2y)+(x²-y)(y+x²)=? (x+y)(x-y)-(x-y)^2如题 (x+y)(x-y)-(x-y)^2