How do I plot a line on a graph, given the equation y=2x+1 ?

A simple way to do this is to use substitution. You can pick values for x such as x=0,1,2 and find the values for y. When you have two or more coordinates you can plot the line.

In this case you could find coordinates (0,1), (1,3), (2,5) and plot the line.

A second and quicker way to do this is to understand the generic equation of a line: y=mx+c and what it represents.

'm' is th gradient on the line and in this case m=2.

'c' is where the line crosses the y axis (when x=0) 

If the line equation is simple then you can quicker inspect the equation and then use the coordinate method to check.

Here's another question to try out either method:

Plot the line y=3x+2