Quiz 8：函數分段定義時極限的求法

\(f(x) = \left\{ {\begin{array}{*{20}{c}}{{x^2} + 3\;,x \ge 4}\\{2x + 6\;,x < 4}\end{array}} \right.\ 則 \lim \limits_{x \to {4^ + }} f(x) = \_\_\_\_\) ？