Linear relationship

A linear relationship is one where equal changes in the independent-variable produce equal changes in the dependent-variable. Written as an equation it has the form y = mx + b, and it graphs as a straight line on a coordinate-plane.

The constant m is the rate of change, the amount y changes per unit of x, and b is the y-intercept, where the line crosses the y-axis. A proportional relationship is the special case that passes through the origin.