设f(u)可导，z=xyf((y)/(x))，若x(partial z)/(partial x)+y(partial z)/(partial y)=xy(lny-lnx)，则 (A.)f(1)=(1)/(2),f^prime(1)=0. (B.)f(1)=0,f^prime(1)=(1)/(2). (C.)f(1)=(1)/(2),f^prime(1)=1. (D.)f(1)=0,f^prime(1)=1.

设 z = f(-(x)/(y))，且 f(x) 可导，则 (partial z)/(partial x) = ( )A. $f'\left(-\frac{x}

设 z = (u)/(x+y)，而 u = e^xy，则 (partial z)/(partial y) = ()A. $\frac{xe^{xy}}{x+y}

若z=f(x,y),x=u+v,y=u-v,则(partial^2z)/(partial upartial v)=(partial^2z)/(partial x

设 =f(x+y,xy), f具有一阶连续偏导数,求 dfrac (partial z)(partial x), dfrac (partial z)(parti

设 =f(xy,(x)^2+(y)^2), 其中 f 可微,则 dfrac (partial z)(partial x)= __

设 z = e^u sin v，而 u = xy，v = x + y，则 (partial z)/(partial x) = ( )A. $z = e^{xy}

设z=sin(uv)，u=x+y，v=x-y，则(partial z)/(partial y)=【】 设$z=\sin(uv)$，$u=x+y$，$v=x-y

设F(x, y, z)= 0定义z为x和y的隐函数，则(partial z)/(partial x)等于（） 设$F(x, y, z)= 0$定义$z$为$x

sin (x+2y-3z)=x+2y-3z, 则 dfrac (partial z)(partial x)+dfrac (partial z)(partial

5.设 sin (x+2y-3z)=x+2y-3z, 证明: dfrac (partial z)(partial x)+dfrac (partial z)(pa