畫出 \(f(x) = \left\{ {\begin{array}{*{20}{c}}{\;2x - 1\;,\;\;\;\;x \le 2}\\{\;\;\;\;{x^2} - 1\quad \;,\;\;\;x{\rm{ > }}2}\end{array}} \right.\) 之圖形，並找出使函數連續之區間