Putting a bar over the variable not the argument or the space between them

Question

I am trying to put the bar on the variable but I either get it on the argument with \bar command or over the whole with \overline. The expression is. Look especially at the derivative and s:

\begin{align*}
\frac{d\bar{x_{1}(\tau)}}{d\tau}=\quad&\bar{x_{1}}\left[\bar{r_{1}}\left(1-\bar{x_{1}}-\bar{\eta_{12}}\bar{x_{2}}-\bar{\eta_{13}}\bar{x_{3}}-\bar{\eta_{14}}\bar{x_{4}}\right)-\bar{f_{11}}\bar{y_{1}}-\bar{f_{12}}\bar{y_{2}} \right] +\bar{s_{i}(\tau)},\quad \bar{x_{1}(0)}>0\\
\end{align*}

Answer 1

\bar places an accent over the argument supplied (\overline is similar but uses a drawn rule of arbitrary length rather than a fixed width accent.

here you want x̄ so \bar{x} with just x in the argument, not \bar{x_{1}{\tau)}