Cases error $ is added

Question

I have read all the posts on this error that I can find. None of the solutions end up with the correct layout that this code does (left aligned, a=1 in rear). My issue is that it throws a $ added error.

\documentclass[12pt]{exam}

\usepackage{amsmath}

\begin{document}

$f(x)=$
\begin{cases} 
    x+2,&  \text{if}\ x\geq 1 \\
    x-2,&  \text{if}\ x<1
\end{cases}, \ \ $a=1$
        
\end{document}

Answer 1

The cases environment should be in math mode. (It doesn't start math mode itself.)

\documentclass[12pt]{exam}

\usepackage{amsmath}

\begin{document}

\(f(x)=
\begin{cases}
    x+2,&  \text{if } x\geq 1 \\
    x-2,&  \text{if } x<1
\end{cases}, \quad a=1\)
        
\end{document}

Switch \( and \) to \[ and \] if you want display math.