Answer
Please see the graph.
Work Step by Step
Red line: $g(x)=2x+1$
Green line: $f(x)=2x$
If we let $x=0$, then we have the two following points.
$g(x)=2x+1$
$g(0)=2*0+1$
$g(0)=0+1$
$g(0)=1$
$f(x)=2x$
$f(0)=2*0$
$f(0)=0$
If we let $x=1$, then we have the two following points.
$g(x)=2x+1$
$g(1)=2*1+1$
$g(1)=2+1$
$g(1)=3$
$f(x)=2x$
$f(1)=2*1$
$f(1)=2$
The two lines have the same slope, so they are parallel.