1. 3-5 & 3-6
Lines in the Coordinate Plane & Slopes of Parallel and Perpendicular Lines

2. OBJECTIVES To graph lines given their equations
To write equations of lines
To relate slope to parallel and perpendicular lines

3. Equations of Lines
Slope-Intercept Form y = mx + b m = slope b = y-intercept (x,y) is any point on that line Standard Form of a Line Ax + By = C Step 1: Find y-intercept, substitute 0 for x; solve for y Step 2: Find x-intercept, substitute 0 for y; solve for x Step 3: Plot two intercepts and draw the line As an alternative, you can transform standard form into slope-intercept form.
Point-Slope Form- used to find the equation of a line given a point and the slope y-y1 = m(x-x1) m = slope (x1.y1) is a specific point on the line Slope- m = y2 – y1/x2 – x1 Rise/run Change in y/change in x

4. Slopes of Parallel Lines
If two nonvertical lines are parallel, their slopes are equal
If the slopes of two distinct nonvertical lines are equal, the lines are parallel
Any two vertical lines are parallel

5. Slopes of Perpendicular Lines
If two nonvertical lines are perpendicular, the product of their slopes is -1
If the slopes of two lines have a product of -1, the lines are perpendicular
Any horizontal line and vertical line are perpendicular