\[ f(x + h) \approx f(x) +\nabla f(x) \cdot h \]

\[ L(x,\lambda) = f(x) + \lambda g(x) \]

\[ \nabla f(x) = \left( \begin{array}{c} \frac{\partial f}{\partial x_1}(x) \\ \vdots \\ \frac{\partial f}{\partial x_n}(x) \end{array} \right) \]