how to find the slope of two points
To find the slope between two points, you use a simple formula that measures how steep the line is that connects them.
Core idea
If you have two points on a line:
- First point: (x1,y1)(x_1,y_1)(x1β,y1β)
- Second point: (x2,y2)(x_2,y_2)(x2β,y2β)
Then the slope mmm is:
m=y2βy1x2βx1m=\frac{y_2-y_1}{x_2-x_1}m=x2ββx1βy2ββy1ββ
People often call this βrise over run,β where:
- Rise = change in y = y2βy1y_2-y_1y2ββy1β
- Run = change in x = x2βx1x_2-x_1x2ββx1β
Stepβbyβstep example
Say your two points are (1,β2)(1,-2)(1,β2) and (3,β6)(3,-6)(3,β6).
- Label the points:
- (x1,y1)=(1,β2)(x_1,y_1)=(1,-2)(x1β,y1β)=(1,β2)
- (x2,y2)=(3,β6)(x_2,y_2)=(3,-6)(x2β,y2β)=(3,β6)
- Plug into the formula:
m=y2βy1x2βx1=β6β(β2)3β1=β6+22=β42=β2m=\frac{y_2-y_1}{x_2-x_1} =\frac{-6-(-2)}{3-1} =\frac{-6+2}{2} =\frac{-4}{2} =-2m=x2ββx1βy2ββy1ββ=3β1β6β(β2)β=2β6+2β=2β4β=β2
So the slope of the line through those two points is β2-2β2.
Important details and special cases
- It does not matter which point you call βpoint 1β and which βpoint 2,β as long as you stay consistent in the formula (the x and y from the same point must go together).
- If x2βx1=0x_2-x_1=0x2ββx1β=0, that means the line is vertical and the slope is undefined (you cannot divide by zero).
- If y2βy1=0y_2-y_1=0y2ββy1β=0, that means the line is horizontal and the slope is 000.
Quick miniβstory to remember it
Imagine youβre hiking a straight trail on a hill from one marker to another:
- The change in height between markers is your βriseβ (y2βy1y_2-y_1y2ββy1β).
- The distance forward you walk is your βrunβ (x2βx1x_2-x_1x2ββx1β).
- The steepness of the trail is the slope: rise Γ· run.
A positive slope means youβre going uphill as you move to the right; a negative slope means downhill.
Tiny checklist
When youβre given two points and asked βhow to find the slope of two points,β do this:
- Write the two points and label them (x1,y1)(x_1,y_1)(x1β,y1β) and (x2,y2)(x_2,y_2)(x2β,y2β).
- Compute y2βy1y_2-y_1y2ββy1β.
- Compute x2βx1x_2-x_1x2ββx1β.
- Divide: slope m=y2βy1x2βx1m=\dfrac{y_2-y_1}{x_2-x_1}m=x2ββx1βy2ββy1ββ.
- Simplify the fraction and check if the line is vertical (undefined) or horizontal (0).
TL;DR:
Use m=y2βy1x2βx1m=\dfrac{y_2-y_1}{x_2-x_1}m=x2ββx1βy2ββy1ββ, plug in your two
points, and simplify; thatβs exactly how to find the slope of two points in
any basic algebra or graphing problem.
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