数学公式

$\because ln(f_n)=\sum\limits_{i=1}^{m}n_iln(p_i)$

$\begin{equation} \left\{\begin{array}{lr}\frac{\partial ln(f_n)}{\partial p_i}=0& \\~~~~\vdots &\\ \frac{\partial ln(f_n)}{\partial p_m}=0& \end{array} \right. \end{equation}$