f(xy,x-y)=x^2+y^2,则fx(x,y)+fy(x,y)=

f(x+y)=f(x)+f(y)+2xy f(xy,x-y)=x^2+3xy+y^2,则f(x,y)=? f(xy,x-y)=x^2+y^2+xy;f(x,y)/∂x;f(x,y)/∂y 设f（x+y,xy）=x^2+y^2,则f（x,y） 函数f(xy,x+y)=x^2+xy+y^2,则df(x,y)=? f(x+y)+f(xy-1)=f(x)f(y)+2f(n)表达式 设f(x+y,xy)=x^2+y^2-xy,则（∂f(x,y)）/∂y= 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) f(xy)=f(x)+f(y)且f(8)=3则f(2)= f(xy)=f(x)+f(y),f(8)=3,则f(根2)等于 y'=-2xy;求f(x). f(x)满足f(x+y)=f(x)+f(y)+2xy,(x,y属于R),f(1)=2,则f(-3)等于多少 . 已知f(x+y)=f(x)+f(y)+2xy,求f(0) 设f(x+y,x-y)=x^2+xy,求f(x,y) 设f(x+y,y/x)=x^2+y^2,则f(x,y)=?,f(x-y,xy)=? f(x^2-y^2,x-y)=x+y+x^2-xy,求f'(x,y)对y求导