3.2 Exercise 81

Given each function $f ,$ evaluate $f \left(−1\right) , f \left(0\right) , f \left(2\right) ,$ and $f \left(4\right) .$

$f \left(x\right) = \left\{\right. \begin{matrix}7 x + 3 & \text{if} & x < 0 \\ 7 x + 6 & \text{if} & x \geq 0\end{matrix}$