We plot the points (1,2), (2,8), (3,14), (4,20).



We notice that we can draw a straight line through them, like this:



So we find the equation of the line that passes through two of them,
say the first two, (1,2) and (2,8)

find the slope, using the formula:



Then substitute in the point-slope equation:






Now we check to see if (3,14) and (4,20) satisfy the
equation:

Substituting (3,14),



 

So (3,14) satisfies it and is therefore on the line.

Substituting (4,20),



 

So (4,20) satisfies it also and is therefore on the line.

Therefore thew correct equation is



Edwin