f(xy,x-y)=x^2+3xy+y^2,则f(x,y)=?

f(xy,x-y)=x^2+3xy+y^2,则f(x,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-xy+y^2.求f(x,y) y'=-2xy;求f(x). 函数f(xy,x+y)=x^2+xy+y^2,则df(x,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(x,y)=x^2+xy+y^2-3x-6y的极值 |x|/x+y/|y|+xy/|xy|= （-3x^y+2xy)-( )=4x^+xy 高数题!f(x,y)=x^3-2xy+3y^2,求f(x+y,x-y).要借题步骤 设f(x+y,xy)=x^2+y^2-xy,则（∂f(x,y)）/∂y= x*x+xy=3,xy+y*y=2,则x*x+2xy+y*y=________? 设f(x+y,x-y)=x^2+xy,求f(x,y) 当x-y=2xy时,求4x-3xy-4y/xy 【x(xy-xy)-y(x-xy)】÷3xy 若1/x-1/y=2,求3x-2xy-3y/x-xy-y的值3x-2xy-3y/x-xy-y 不好意思，是3x-2xy-3y/x-2xy-y