​Graph the piecewise-defined function at right and determine if the function is continuous at $x=2$. Explain your reasoning.      $f ( x ) = \left\{ \begin{array} { l l } { x ^ { 2 } + x + 1 } & { \text { for } x \leq 2 } \\ { - \frac { 1 } { 2 } x + 7 } & { \text { for } x > 2 } \end{array} \right.$