title: Vertical line in 2d plot using tikzpicture
body: <p>After plotting on overleaf the following right line</p>
  <pre><code>\begin{tikzpicture}
  \begin{axis}[
      axis lines = left,
      xlabel = $x$,
      ylabel = {$f(x)$},
  ]
  %Below the red parabola is defined
  \addplot [
      domain=-10:10, 
      samples=100, 
      color=red,
  ]
  {((6*x - 48)/8)};
  \addlegendentry{$6x + 8y = 48$}
  </code></pre>
  <p>I need to add a vertical line for x = 6 on the same plot.
  Could you help me with that?</p>