Here's the question you clicked on:
b-rye
Write the function as a piecewise function. f(x) = 3x + |x|
Conceptually, it would help you to graph it.
Rember |x|=x when x>=0 and -x when x<0, so you can write it like this: \[ f(x) = \left \{ \begin{matrix} 4x & \mbox{if }x\geq0 \\ 2x & \mbox{if }x<0\end{matrix}\right. \]