Coordinate Geometry & Straight-Line Graphs

Gradient and the equation of a line

The gradient of a line through $(x_1, y_1)$ and $(x_2, y_2)$ is

$$m = \frac{y_2 - y_1}{x_2 - x_1} = \frac{\text{rise}}{\text{run}}$$

The straight-line equation is $y = mx + c$, where $m$ is the gradient and $c$ is the $y$-intercept.