The transformation
[tex]f(x)\longrightarrow j(x)=3f(x)[/tex]
describes a vertical stretch by a factor of 3 as we can note on the following picture:
A vertical compression occurs when the factor is between 0 and 1, for instace, if the factor is 1/4 instead of 3, we have the purple graph g(x):
In the case m(x) =f(3x), we have
[tex]m(x)=|3x|[/tex]
which is equivalent to
[tex]m(x)=3|x|[/tex]
then, in this particular case, the graphs of 3f(x) and f(3x) will be the same.
