求f(x,y)=xy-x^2-y^2+2x+2y的极值?

f(x+y,x-y)=(x^2-y^2)/2xy,求f(x,y)! f(x+y,x-y)=2xy(x-y),求f(x,y) f(xy,x-y)=x^2-xy+y^2.求f(x,y) y'=-2xy;求f(x). 设f(x+y,x-y)=x^2+xy,求f(x,y) f(x^2-y^2,x-y)=x+y+x^2-xy,求f'(x,y)对y求导 f(2x+y,2y+x)=xy,求f(x,y) f(x+y)=f(x)+f(y)+2xy y'=-2xy;求f(x).y'=2y/x+2;求y f(xy,x-y)=x^2+y^2+xy;f(x,y)/∂x;f(x,y)/∂y 已知f(x+y)=f(x)+f(y)+2xy,求f(0) 设函数f(xy,x+y)=x^2+y^2+xy,求∂f(x,y)／∂x和∂f(x,y)／∂y 高数题!f(x,y)=x^3-2xy+3y^2,求f(x+y,x-y).要借题步骤 求f(x,y)=xy-x^2-y^2+2x+2y的极值? 求f(x,y)=xy(x^2-y^2)/(x^2+y^2)偏导数 函数f(xy,y^2/x)=x^2+y^2,求f(y^2/x,xy) 设F(xy,y^2/x)=x^2+y^2,求F（y^2/x,xy） 已知f(xy,（y^2）/x)=x^2+y^2,求f（（y^2）/x,xy）