Slope Vocabulary

zero slope

0/run

undefined slope

rise/0

rise/run

the measure of the steepness of a line

y - y₁ = m(x - x₁)

m is the slope of the line

(x₁,y₁) are the coordinates of the point the line goes through

y = mx + b

m is the slope of the line

b is the y-intercept

Ax + By = C

Slope is not given by this form directly.

• You must solve the equation for y =,
• then m = -A/B.

• y₂ - y₁ = m
• x₂ - x₁

This is the formula to find the slope of a line given two points.

Parallel lines are two lines that never intersect.

Their slopes are equal.

Perpendicular lines are two lines that intersect at right angles.

Their slopes are opposite reciprocals of each other.

The product of their slopes equals -1.

m = -3

Undefined slope

The line is vertical.

m = 2

The slopes are the same.

m = -4/3

The equation is y = -4/3 x + 4

zero

The line is horizontal.

m = 0.5

The line goes through (-3, -4).

The slope of this line is 4/3, so the perpendicular slope is the opposite reciprocal: -3/4.

• -3 - 4 = -7 = m
• 0 - -2 2