\begin{frame}{Exercises (1)} % (Groups of two, 1 minute) \begin{exampleblock}{} \emph{Show that the following language is context-free:} \begin{talign} \{\, a^n\, b^m\, c^{2n} \mid n\geq 0,\; m\ge 0 \,\} \end{talign} \pause We give a context-free grammar for the language: \pause \begin{align*} S &\to aScc \mpause[1]{\mid T} \\ \mpause{T &\to bT \mid \lambda} \end{align*} The start variable is $S$. \end{exampleblock} % (Groups of two, 1 minute) \end{frame}