Understanding Slope as Rise over Run
The slope of a line measures its steepness. It is often described as "rise over run".
- Rise: This is the vertical change between two points on the line (how much it goes up or down).
- Run: This is the horizontal change between the same two points (how much it goes left or right).

A positive slope means the line goes up from left to right. A negative slope means the line goes down from left to right.

Calculating the Slope from Two Points
If you know two points on a line, $(x_1, y_1)$ and $(x_2, y_2)$, you can calculate the slope (denoted by the letter m) using the formula:
$m = \frac{\text{Rise}}{\text{Run}} = \frac{y_2 - y_1}{x_2 - x_1}$
Example: Let's find the slope of a line passing through the points $(-8, 3)$ and $(-2, -12)$.
- Identify your points: $(x_1, y_1) = (-8, 3)$ and $(x_2, y_2) = (-2, -12)$.
- Plug the values into the formula. This calculation involves adding and subtracting negative and positive integers. $m = \frac{-12 - 3}{-2 - (-8)}$
- Simplify the numerator and the denominator: $m = \frac{-15}{-2 + 8} = \frac{-15}{6}$
- Reduce the fraction to its simplest form: $m = -\frac{5}{2}$
So, the slope of the line is $-\frac{5}{2}$.
Identifying and Finding Intercepts
The intercepts are the points where a line crosses the axes of the coordinate plane.
- x-intercept: The point where the line crosses the horizontal x-axis. At this point, the y-coordinate is always 0. It has the form $(x, 0)$.
- y-intercept: The point where the line crosses the vertical y-axis. At this point, the x-coordinate is always 0. It has the form $(0, y)$.
Finding Intercepts from an Equation
To find the intercepts from a linear equation (like $Ax + By = C$):
- To find the y-intercept: Set $x=0$ in the equation and solve for $y$.
- To find the x-intercept: Set $y=0$ in the equation and solve for $x$.
Example: Find the intercepts for the equation $4x - 5y = 20$.
- Find y-intercept (set x = 0): $4(0) - 5y = 20$ $-5y = 20$ $y = -4$ The y-intercept is at the point $(0, -4)$.
- Find x-intercept (set y = 0): $4x - 5(0) = 20$ $4x = 20$ $x = 5$ The x-intercept is at the point $(5, 0)$.