题目
设z=f(xy,x^2+y^2)，其中f(u,v)有二阶连续偏导数，则(partial^2z)/(partial xpartial y)=（ ）A. f_(1)'+xyf_(11)''+4xyf_(22)''B. f_(1)'+xyf_(11)''+2(x^2+y^2)f_(12)''+4xyf_(22)''C. xyf_(11)''+2(x^2+y^2)f_(12)''+4xyf_(22)''D. xyf_(11)''+4xyf_(22)''
设$z=f(xy,x^{2}+y^{2})$，其中$f(u,v)$有二阶连续偏导数，则$\frac{\partial^{2}z}{\partial x\partial y}=$（ ）
A. $f_{1}'+xyf_{11}''+4xyf_{22}''$
B. $f_{1}'+xyf_{11}''+2(x^{2}+y^{2})f_{12}''+4xyf_{22}''$
C. $xyf_{11}''+2(x^{2}+y^{2})f_{12}''+4xyf_{22}''$
D. $xyf_{11}''+4xyf_{22}''$
题目解答
答案
B. $f_{1}'+xyf_{11}''+2(x^{2}+y^{2})f_{12}''+4xyf_{22}''$