Vertical compression of a function is moving the graph of the function towards the x axis.
It is done by multiplying F(x) with IaI<1, the absolute value of a is less than 1. Then we get f(x)=a*F(x).
If we have a function F(x)=x, and we multiply it by a=1/2, we get:
f(x)=a*F(x)=a*x=(1/2)*x.
This linear function is vertically compressed because the the graph of a new function is closer to the x axis.
