I am trying to code an equation into LaTeX but I keep getting this error. I found some similar questions, but the solutions given are also not working.

I'm working in a documentclass report. I also tried the code in article and book. I'm also using the package amsmath.

$\Pi_W$  =  \large{$\frac {(c\rho)^c}{1 - \rho}$}\\
 \notag & = \large{$\frac {(c\rho)^c}{c!} \bigg( {(1-\rho)} \sum_{n=0}^{c-1} \frac {(c\rho)^n}{n!} + \frac {(c\rho)^c}{c!}$ \bigg) ^{-1}}

This is the equation I'm trying to get, beginning the second part. Also I only want the second line to have an equation number. enter image description here

Note: I'm very new with LaTeX.

What did I do wrong?

  • 1
    Welcome to TeX.SX! Please make your code compilable (if possible), or at least complete it with \documentclass{...}, the required \usepackage's, \begin{document}, and \end{document}. That may seem tedious to you, but think of the extra work it represents for TeX.SX users willing to give you a hand. Help them help you: remove that one hurdle between you and a solution to your problem.
    – TobiBS
    Sep 14, 2020 at 8:10
  • @TobiBS Thank You for the tip. I'll keep that in mind next tuime.
    – MaineRo
    Sep 14, 2020 at 8:19

1 Answer 1


There are two problems with that. In the first place, what are those $ signs doing there? In the second place, you cannot use \large in math mode.

This will compile without errors:

\Pi_W  &=  \frac {(c\rho)^c}{1 - \rho}\\
 \notag & = \frac {(c\rho)^c}{c!} \bigg( {(1-\rho)} \sum_{n=0}^{c-1} \frac {(c\rho)^n}{n!} + \frac {(c\rho)^c}{c!} \bigg) ^{-1}

The next time, I suggest that you post a minimal working example.

  • I use \large because the equation was very small in my pdf document. The & I left there by accident, while copying and pasting.
    – MaineRo
    Sep 14, 2020 at 8:25
  • Thank you for the solution. I can't believe it was that simple.
    – MaineRo
    Sep 14, 2020 at 8:28
  • May I suggest to use the pair \biggl( … \biggr)?
    – Bernard
    Sep 14, 2020 at 8:31

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