Grade 8 · Expressions and Equations

CCSS.MATH.CONTENT.8.EE.B.6

Use similar triangles to explain why the slope m is the same between any two distinct points on a non-vertical line in the coordinate plane; derive the equation y = mx for a line through the origin and the equation y = mx + b for a line intercepting the vertical axis at b.

Read this standard on the official Common Core site

Lessons that teach this standard

• What Slope Is, and Why It Never Changes on a Line

  Learn what slope measures, how to find it with rise over run and the slope formula, and why similar triangles guarantee it is the same everywhere on a line.

• How to Write the Equation of a Line from Two Points

  Find a line's equation from any two points: compute the slope, substitute into point-slope form, then simplify — with worked examples and full solutions.