1. Lesson 3-7: Parallel & Perpendicular Lines Objectives Students will: Use equations to determine if two lines are parallel or perpendicular Write an equation of a line that is parallel or perpendicular to a given line

2. Graph the following lines y = 2x + 1 2x – y = 3 (solve for y) What do you notice about the slopes? What do you notice about the lines? What do you notice about the slopes? What do you notice about the lines? (solve for y)

3. Look at the slopes from the graphs: Parallel lines → same slope Perpendicular line → “opposite reciprocal” slope Writing Equations 1)Get the slope you want 2)Plug it to point-slope then solve for y (slope-intercept) Remember: In standard form the slope is

4. Example 1: y = 5x + 2 ; y = -5x + 2 Parallel, perpendicular, or neither? m=5 and m= -5 not same so not parallel Opposite but not reciprocals so not perpendicular So neither

5. Example 2: Write an equation for a line parallel to y = 5x + 4 through (1, 3) What slope do we have? What slope will we use? Use point-slope then rearrange to slope-intercept!!

6. Example 3: Write an equation for a line perpendicular to 3x + 4y = 5 through (3, -2) What slope is this line? What slope will you use? Use point-slope then rearrange to slope-intercept.