求f(x.y)=x^2+y^2-2x-2y-1的最大和最小值.x^2+y^2x≤25

f(x+y,x-y)=(x^2-y^2)/2xy,求f(x,y)! f(x+y,y/x)=x^2-y^2求f(x,y) f(x+y,y/x)=x^2-y^2,求f(x,y),详见里面 f(x+y,x-y)=2xy(x-y),求f(x,y) f(x^2-y^2,x-y)=x+y+x^2-xy,求f'(x,y)对y求导 设f(x+y,x-y)=x^2+y^2-x*y求f(x,y) 设f(x+y,x-y)=x^2+xy,求f(x,y) 英国数学竞赛题.f(x,x)=x,f(x,y)=f(y,x),(x+y)*f(x,y)=(2x+y)*f(x,x+y)求f(19,91) f(2x+y,2y+x)=xy,求f(x,y) f(xy,x-y)=x^2-xy+y^2.求f(x,y) 已知f(0)=1,f(x-y)=f(x)-y(2x-y+1),求f(x) 高数题!f(x,y)=x^3-2xy+3y^2,求f(x+y,x-y).要借题步骤 f(x^2-y^2,x-y)=x+y+x^2-xy,求fy(x,y)的导数. 设y=f(x),f'(x)存在,求y=f(2^x)的导数 导数：f(x+y)=f(x)f(y),且f'(o)=1,求f'(x)f(x+y)=f(x)f(y),且f'(o)=1,求f'(x)f(x+y)=f(x)+f(y)+2xy,且f'(o)存在,求f'(x) f(1+x)=af(x),且f'(0)=b,求f'(1) 设f(x+y,x-y)=x^2-y^2,则f(x,y)= 若f(x+y,y/x)=x^2-y^2,则F(X,Y)= 已知f(x+y,y/x)=x^2-y^2,则f(x,y)=