3.[判断题] 例4 设w=f(x+y+z,xyz)，f具有二阶连续偏导数 解 令u=x+y+z，v=xyz，则w=f(u,v). 则 (partial w)/(partial y)=(partial f)/(partial u)cdot(partial u)/(partial y)+(partial f)/(partial v)cdot(partial v)/(partial y)=f_(u)+xzf_(v)A. 对B. 错

3.[判断题] 例4 设w=f(x+y+z,xyz)，f具有二阶连续偏导数 解 令u=x+y+z，v=xyz，则w=f(u,v). 则 $\frac{\partial w}{\partial y}=\frac{\partial f}{\partial u}\cdot\frac{\partial u}{\partial y}+\frac{\partial f}{\partial v}\cdot\frac{\partial v}{\partial y}=f_{u}+xzf_{v}$

A. 对

B. 错