题目
已知u=f(x+2y,y-3z,z+4x)，其中函数f有二阶连续偏导数，则(partial^2 u)/(partial y partial z)=（）A. (partial^2 u)/(partial y partial z)=6f_(12)''+2f_(13)''+3f_(22)''+f_(23)''B. (partial^2 u)/(partial y partial z)=-6f_(12)''-3f_(22)''C. (partial^2 u)/(partial y partial z)=-6f_(12)''+f_(13)''-3f_(22)''+f_(23)''D. (partial^2 u)/(partial y partial z)=-6f_(12)''+2f_(13)''-3f_(22)''+f_(23)''
已知$u=f(x+2y,y-3z,z+4x)$，其中函数$f$有二阶连续偏导数，则$\frac{\partial^2 u}{\partial y \partial z}=$（）
A. $\frac{\partial^2 u}{\partial y \partial z}=6f_{12}''+2f_{13}''+3f_{22}''+f_{23}''$
B. $\frac{\partial^2 u}{\partial y \partial z}=-6f_{12}''-3f_{22}''$
C. $\frac{\partial^2 u}{\partial y \partial z}=-6f_{12}''+f_{13}''-3f_{22}''+f_{23}''$
D. $\frac{\partial^2 u}{\partial y \partial z}=-6f_{12}''+2f_{13}''-3f_{22}''+f_{23}''$
题目解答
答案
D. $\frac{\partial^2 u}{\partial y \partial z}=-6f_{12}''+2f_{13}''-3f_{22}''+f_{23}''$