By definition, a single line passes through two points, then you can give x two values to obtain two points of the line and thus be able to graph it.
Then, if for example you take x = 2 and x = 3 you have
[tex]\begin{gathered} \text{If x=2} \\ y=3x+1 \\ y=3(2)+1 \\ y=6+1 \\ y=7 \\ \text{ So, if x = 2 you have the point (2,7)} \end{gathered}[/tex][tex]\begin{gathered} \text{If x=3} \\ y=3x+1 \\ y=3(3)+1 \\ y=9+1 \\ y=10 \\ \text{ So, if x = 3 you have the point (3,10)} \end{gathered}[/tex]Now graphing you have
