CCLS - Math: 8.EE.6

Expressions And Equations
Understand The Connections Between Proportional Relationships, Lines, And Linear Equations.
State Standard:
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.