According to the graph, we have:
[tex]f(x)=\begin{cases}\frac{1}{3}x+1{,\text{ if }x\leq3} \\ \frac{7}{2}x-\frac{21}{2},\text{ if }x>3{}\end{cases}[/tex]
Then, we have:
[tex]f(3x)=\begin{cases}{x+1},\text{ if }x\leq1 \\ \frac{21}{2}(x-1),\text{ if}x>1{}\end{cases}[/tex]
This function is represented by:
