1. Equations of Lines Standard Form: Slope Intercept Form: where m is the slope and b is the y-intercept

2. Slopes of Lines Given the points (x 1, y 1 ) and (x 2, y 2 ) on a line, its slope is

3. If the slope is positive the line is increasing: If the slope is negative the line is decreasing: Slopes of Lines

4. If the slope is zero the line is horizontal: If the slope is undefined the line is vertical:

5. Slopes of Lines If two lines are parallel their slopes are equal. If two lines are perpendicular their slopes are negative reciprocals.

6. Graphing Lines The x-intercept is the point where the line crosses the x-axis, found by setting y = 0 and solving for x. The y-intercept is the point where the line crosses the y-axis, found by setting x = 0.