函数f(xy,x+y)=x^2+xy+y^2,则df(x,y)=?

函数f(xy,x+y)=x^2+xy+y^2,则df(x,y)=? 函数f(xy,y^2/x)=x^2+y^2,求f(y^2/x,xy) 设函数f(xy,x+y)=x^2+y^2+xy,求∂f(x,y)／∂x和∂f(x,y)／∂y f(x+y)=f(x)+f(y)+2xy f(xy,x-y)=x^2+y^2+xy;f(x,y)/∂x;f(x,y)/∂y f(xy,x-y)=x^2+3xy+y^2,则f(x,y)=? f(xy,x-y)=x^2-xy+y^2.求f(x,y) 函数x^y=xy能否给出表达式f(x) y'=-2xy;求f(x). 求函数f(x,y)=x^2-xy+y-3x的极值 函数f(x,y)=xy/x*2 y*2,求limf(x,y)与limf(x,y) 设函数f(x,y)=xy/根号x^2+y^2,求limf(x,y)x,y趋于0 f(x)满足f(x+y)+f(xy)=2f(x)f(y)求函数的奇偶性 已知二元函数f(x+y,xy)=x²+y²,求f(x,y). 函数y=f(x)由方程xy^2+sinx=e^y,求y′ f(x+y,x-y)=(x^2-y^2)/2xy,求f(x,y)! 高数求函数f(x,y)=xy(x^2+y^2-1)的极值 求函数f(x,y)=xy(x^2+y^2-4)的极值