Heuristics to highlight

Use suitable numbers (instead of algebra), Think of a related problem, Divide into cases.

It is given that \[|x|\text{ }=\left\{ \begin{matrix} x & \text{if }x\ge 0; \\ -x & \text{otherwise}\text{.} \\ \end{matrix} \right.\]Sketch the graph of \[y=3\left| x \right|-4\].