1. Bellwork
Partner Activity for graphing

2. Algebra 2 Lesson 1.3 Day 2 Linear Equations in two variables
Parallel and Perpendicular Lines

3. Objectives:
Write an equation for a line that is parallel or perpendicular to a given line.

4. Results from partner activity.
Parallel Lines
Two lines that have the same slope are parallel.
All horizontal lines are parallel.
All vertical lines are parallel.
Perpendicular Lines
The slopes of perpendicular lines are negative reciprocals of each other.
All vertical lines are perpendicular to horizontal lines.
All horizontal lines are perpendicular to vertical lines.

5. Practice: Identify parallel, perpendicular and intersecting Lines
1.) y = 2x+4 and y = -½x - 6
Answer: Perpendicular lines
2.) y = -3 and y = 4
Answer: Parallel lines
3.) y = 2x – 6 and x = 3
Answer: Intersecting lines
4.) y = ¼x + 7 and y + 4x = 2
5.) y -4x = 23 and 2y – 8x = 16
Answer: Parallel lines

6. Key Concept: Use your knowledge of parallel and perpendicular slopes to write equations of line.
You will still use the slope-intercept equation or the point-slope equation when writing the equations.

7. Example
Write in slope intercept form the equation of the line that is parallel to the line
in the standard (x,y) plane an
that also contains the point (4, -2).
1st step: find the slope
2nd step: find the y-intercept
y = mx+b
-2 = (1/2)(4) +b
b = -4
3rd step: write the equation
y = (1/2)x - 4

8. Try These
Directions: Write an equation in slope intercept form for the line that has the given information.
Passing through (8, 5) and parallel to
Answer:
Passing through (-2, -5) and perpendicular to
Contains the y-intercept of the line and is perpendicular to the line

9. Homework Lesson 1.3 Page 26 (35-51 odds, 53-58 all)
Be sure to show all work and check your answers with b.o.b.