When \( a \ne 0 \), there are two solutions to \( ax^2 + bx + c =0 \) and they are

\[x = { -b \pm \sqrt{b^2-4ac} \over 2a }.\]

今天遇到一个分段函数，貌似codecogs是不支持的，试试用MathJax来写。

\[L_{ti} = \left \{ \begin{array}{ll} L_{t0i}+\lambda_{pvi}\overline{L_{pi}}+\lambda_{fvi}\overline{L_{fi}}, & t\in T_v \\\\ L_{t0i}+\lambda_{pfi}\overline{L_{pi}}-\lambda_{fvi}\overline{L_{fi}}, & t\in T_f \\\\ L_{t0i}-\lambda_{pvi}\overline{L_{pi}}-\lambda_{pfi}\overline{L_{pi}}, & t\in T_p \end{array} \right.\]