Section 1 2 Straight Lines Straight Lines Slope

Section 1. 2 Straight Lines

Straight Lines • Slope • Point-Slope Form • Slope-Intercept Form • General Form

Slope – the slope of a non-vertical line that passes through the points is given by: and Ex. Find the slope of the line that passes through the points (4, 0) and (6, -3)

Slope Two lines are parallel if and only if their slopes are equal or both undefined Two lines are perpendicular if and only if the product of their slopes is – 1. That is, one slope is the opposite sign and reciprocal of the other slope (ex. ).

Point-Slope Form An equation of a line that passes through the point with slope m is given by: Ex. Find an equation of the line that passes through (3, 1) and has slope m = 4

Slope-Intercept Form An equation of a line with slope m and y-intercept can be given by: Ex. Find an equation of the line that passes through (0, -4) and has slope .

General Form The general form of an equation of a line is given by: Where A, B, and C are constants and A and B are not both zero. *Note: An equation of a straight line is a linear equation and every linear equation represents a straight line.

Vertical Lines Can be expressed in the form x = a x=3

Horizontal Lines Can be expressed in the form y = b y=2

Ex. Find an equation of the line that passes through the point (– 2, 3) and is parallel to the y – axis. y-axis (– 2, 3) Vertical Line: x = – 2