[Tex/LaTex] Can’t recognize math symbol – bold “minus” above variable

math-modesymbols

I'm trying to "latex down" some Kalman equations and I'm not able find a way how to make that symbol above k variable in equation "Predict" (1) and (2)
picture

For me, it seems like \bar{} but still I wasn't able to make it look like the same.

Best Answer

% arara: pdflatex

\documentclass{article}

\begin{document}
\[\hat{x}^{-}_{k}=A\hat{x}_{k-1}+Bu_k \]
\end{document}

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