The Algebra of Lines:

How to Find the Slope of a Line Between Two Points

Slope measures the steepness of a line or the rise divided by the run. Another way to think of this is the comparison of the amount a line goes up or down compared to how much it changes left or right between two points. This is shown as a step. This is also known as the rate of change of a line. The following video will go over how to find the slope, especially when it’s hard to just look to see how far up and over the graph goes.

Video Source (07:26 mins) | Transcript

The following video shows another example of using the formula taught in the previous video.

Video Source (03:37 mins) | Transcript

\({\text{Slope}}={\text{m}}=\frac{\text{rise}}{\text{run}}=\frac{{\text{y}}_{2}-{\text{y}}_{1}}{{\text{x}}_{2}-{\text{x}}_{1}}\)

Be sure to keep track of which point is point 1=\(({\text{x}}_{1},{\text{y}}_{1})\) and which is point 2=\(({\text{x}}_{2},{\text{y}}_{2})\) because it’s important that we are consistent with which one comes first in our formula.

Additional Resources

Practice Problems

  1. Find the slope of the line that contains the points \((10, -9)\) and \((7, 6)\).
  2. Find the slope of the line that contains the points \((10, -1)\) and \((14, -9)\).
  3. Find the slope of the line that contains the points \((10, 0)\) and \((17, -42)\).
  4. Find the slope of the line that contains the points \((3, 5)\) and \((13, 20)\).
  5. Find the slope of the line that contains the points \((-8, 10)\) and \((-32, 2)\).
  6. Find the slope of the line that contains the points \((8, -9)\) and \((-27, -30)\).

Solutions

  1. \(-5\) (Written Solution)

  2. \(-2\)

  3. \(-6\)

  4. \(\frac{3}{2}\) (Written Solution)

  5. \(\frac{1}{3}\)

  6. \(\frac{3}{5}\)