x^2-xy-2y^2-x-y=?.

f(xy,x-y)=x^2+y^2+xy;f(x,y)/∂x;f(x,y)/∂y (-x-y)(x^2+xy+y^2) 化简x^-y^/x^-2xy+y^ 2*(x-y)²(y-x)(xy) x*x+xy=3,xy+y*y=2,则x*x+2xy+y*y=________? （x^2+xy/x-y)/（xy/x-y)计算 已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值? (-x+2y)(2x+y)-(2x+y)(y-2x)-3xy=?因式分解 f(x+y,x-y)=(x^2-y^2)/2xy,求f(x,y)! x+y=-3 xy+x+y=-2 x/y+y/x=? 正数x,y满足x-y=2xy,求x-y/x+y的值. f(x+y,x-y)=2xy(x-y),求f(x,y) x^2+xy+x=36,y^2+xy+y=20,求x+y. 若x^2+xy+y=14,y^2+xy+x=28,求x+y 函数f(xy,x+y)=x^2+xy+y^2,则df(x,y)=? f(xy,x-y)=x^2+3xy+y^2,则f(x,y)=? X-Y/2X+2Y XY/X+Y² 因式分解：x×x-xy-2y×y-x-y