Cho hàm số \(f\left( x \right) = \left\{ \begin{array}{l}\dfrac{{\sqrt {x + 4} - 1}}{{x - 1}}\,\,\,khi\,\,\,x > 4\\3 - x\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,khi\,\,\,\,x \le 4\end{ar...

* Hướng dẫn giải

Ta có:\(\left\{ \begin{array}{l}f\left( 5 \right) = \dfrac{{\sqrt {5 + 4}  - 1}}{{5 - 1}} = \dfrac{1}{2}\\f\left( { - 5} \right) = 3 - \left( { - 5} \right) = 8\end{array} \right.\) \( \Rightarrow f\left( 5 \right) + f\left( { - 5} \right) = \dfrac{1}{2} + 8 = \dfrac{{17}}{2}.\)

Đáp án  C.