This is LaTeX code:

[latex]
\overrightarrow{OT} + \overrightarrow{OA_0}=\overrightarrow{OA_0} - \sum_{i=1}^{n}\beta_i \overrightarrow{OA_0}+ \sum_{i=1}^{n}\beta_i \overrightarrow{OA_i}
[/latex]