三元函数求单条件极值:拉格朗日函数的使用(B013)

问题

若要求函数 $u$ $=$ $f(x, y, z)$ 在 $\varphi(x, y, z)$ $=$ $0$ 条件下的极值,且已经构造出了如下的拉格朗日函数:

$F(x, y, z)$ $=$ $f(x, y, z)$ $+$ $\lambda$ $\varphi(x, y, z)$

则,根据拉格朗日乘数法,还需要构造以下哪个选项中的方程组并计算才可能得出与极值对应的驻点 $(x_{0}, y_{0}, z_{0})$ ?

选项

[A].   $\left\{\begin{array}{l}f(x, y, z)+\lambda \varphi_{x}^{\prime}(x, y, z)=0, \\ f(x, y, z)+\lambda \varphi_{y}^{\prime}(x, y, z)=0, \\ f(x, y, z)+\lambda \varphi_{z}^{\prime}(x, y, z)=0, \\ \varphi(x, y, z)=0. \end{array}\right.$

[B].   $\left\{\begin{array}{l}f_{x}^{\prime}(x, y, z)+\lambda \varphi_{x}^{\prime}(x, y, z)=1, \\ f_{y}^{\prime}(x, y, z)+\lambda \varphi_{y}^{\prime}(x, y, z)=1, \\ f_{x}^{\prime}(x, y, z)+\lambda \varphi_{z}^{\prime}(x, y, z)=1, \\ \varphi(x, y, z)=1. \end{array}\right.$

[C].   $\left\{\begin{array}{l}f_{x}^{\prime}(x, y, z)+\lambda \varphi_{x}^{\prime}(x, y, z)=0, \\ f_{y}^{\prime}(x, y, z)+\lambda \varphi_{y}^{\prime}(x, y, z)=0, \\ f_{x}^{\prime}(x, y, z)+\lambda \varphi_{z}^{\prime}(x, y, z)=0, \\ \varphi(x, y, z)=0. \end{array}\right.$

[D].   $\left\{\begin{array}{l}f_{x}^{\prime}(x, y, z)+\lambda \varphi(x, y, z)=0, \\ f_{y}^{\prime}(x, y, z)+\lambda \varphi(x, y, z)=0, \\ f_{x}^{\prime}(x, y, z)+\lambda \varphi(x, y, z)=0, \\ \varphi(x, y, z)=0. \end{array}\right.$


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$\left\{\begin{array}{l}f_{x}^{\prime}(x, y, z)+\lambda \varphi_{x}^{\prime}(x, y, z)=0, \\ f_{y}^{\prime}(x, y, z)+\lambda \varphi_{y}^{\prime}(x, y, z)=0, \\ f_{x}^{\prime}(x, y, z)+\lambda \varphi_{z}^{\prime}(x, y, z)=0, \\ \varphi(x, y, z)=0. \end{array}\right.$


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