设u=f(x,y)可微,且满足方程x(σ f/σ x)+y(σ f/σ y)=0

设u=f(x,y)可微,且满足方程x(σ f/σ x)+y(σ f/σ y)=0 设y=y(x)由方程xe^f(y)=e^y确定,f(u)可导且f′≠1,求dy/dx 设f(x)在x=0处可导,且对任意x.y满足f(x+y)=f(x)f(y),证明f(x)处处可导,且 已知函数f(x)满足f(x+y)+f(x-y)=2f(x)f(y)(x∈R,y∈R),且f(0)≠1. 设y=y(x)由方程xe^f(u)=e^y确定,其中f的二阶可导,且f'≠1求d^2(y)/dx^2 设方程f(xz,yz)=0可确定z是x,y的函数,且f(u,v）具有连续偏导数,求dz, 设f(x)是R上的函数,且满足f(0)=1,且对x,y∈R都有f(x-y)=f(x)-y(2x-y+1),则f(x)的表 设F为三元可微函数,u=u(x,y,z)是由方程F(u^2-x^2,u^2-y^2,u^2-z^2)=0确定的隐函数,求 设函数f（x）满足f(0)=1,且对任意x,y属于R,都有f(xy+1)=f(x)乘f(y)减f(y)减x加2.求f(x 设 z=xyf(y/x),f(u)可导,则xZ'x+yZ'y=? 已知f(x)对任意x、y（属于R）满足f(x)+f(y)=f(x+y) 且当x>0时,f(x) 设f(x,y)=xy+f(u,v)dudv,