Determine Whether the Rule Describes a Function with the Given

Short Answer

determine whether the rule describes a function with the given domain and codomain.
- $$f : \mathbf { R } \rightarrow \mathbf { R } , \text { where } f ( x ) = \left\{ \begin{array} { l l } x ^ { 2 } & \text { if } x \leq 2 \\x - 1 & \text { if } x \geq 4\end{array} \right.$$