Below is a snippet of my latex source that prints an equation. In the attached image output, I see a significant decrease in font size in the part of the equation that is represented as in the numerator/denominator form.
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[
P[Y=l]=
\begin{cases}
\mu(lm+\mu)^{l-1}\frac{{e^{-lm-\mu}}}{r!(1-e^{-\mu})}}; & 1\leq l < M\\
1-\sum_{s=1}^{M-1}\mu(sm+\mu)^{s-1}\frac{{e^{-sm-\mu}}}{s!(1-e^{-\mu})}; & l=M }\\
\end{cases}
\eqno{\hbox{(11)}}\\
\]
\end{document}

Can I force latex to print all parts of the equation in the same font size?
thanks
\displaystyle\frac{}{}– Sigur Dec 18 '14 at 16:56! Extra }, or forgotten $.If you carry on after an error only use the resulting pdf for debugging purposes TeX does not attempt to produce reasonable output, just to get out of an error state – David Carlisle Dec 18 '14 at 16:59\usepackage{mathtools}in the preamble and\begin{dcases}...\end{dcases}instead ofcases. *Never* use\eqnowith LaTeX. – egreg Dec 18 '14 at 16:59