The equation I gave you is in fact a *linear equation*. It has a constant slope. I would say that most mathematicians would agree that a linear equation would give you a straight line.

Let’s say we have 3 points: (0,1), (74,75), & (99,100)

If slope can be represented as M in an equation, and we assume the line is straight, we will see that slope for a linear equation is:

M = Y2 – Y1

X2 – X1

If we plug in the first two points [(0,1) & (74,75)] into the equation above, we will get

M_{1} = (75 - 1) = 1 = 1

(74 - 0) 1

Now, if the slope between points 1 & 3 or 2 & 3 are any different from what we calculated, than it will be proof that the line isn’t linear.

Now, let’s finish this thing and figure out if the line is in fact straight.

M_{2} = (100 - 1) = 1 = 1

(99 - 0) 1

M_{3} = (100 - 75) = 25 = 1

(99 - 74) 25

Now, do the slopes equal each other?

They do! Who would have thought…