Insert formula between lines in latex

1, Enter formula:
Inline formula: < /span> 、< /span> come in.  some person ：Also used Free number line formula；，Example:Line-time formula (self-formula name);$公式$、Example: $\frac{L^4}{2}+\frac{L^3}{6}-\frac{4L}{3}$
\begin{equation}公式\end{equation}\begin{equation} \frac{L^4}{2}+\frac{L^3}{6}-\frac{4L}{3} \end{equation}
\begin{displaymath} ... \end{displaymath}\begin{equation*} ... \end{equation*}

2, Bold (vector or matrix): use \mathbf{} (sometimes \textbf{} is still useful); a>

3, Superscript: letter ^ superscript; subscript: letter _ subscript;

4, Brackets:\left(bracket content\right) or enter () directly;

5,Fraction:\frac{numerator}{denominator};