BELLWORK Partner Activity for graphing

ALGEBRA 2Lesson 1.3 Day 2

Linear Equations in two variables

Parallel and Perpendicular Lines

OBJECTIVES:

• Write an equation for a line that is parallel or perpendicular to a given line.

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.

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 Answer: Perpendicular lines 5.) y -4x = 23 and 2y – 8x = 16 Answer: Parallel lines

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.

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).

18

2y x

1st step: find the slope

2nd step: find the y-intercepty = mx+b-2 = (1/2)(4) +bb = -4

3rd step: write the equationy = (1/2)x - 4

1

2m

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

Answer:

Contains the y-intercept of the line and is perpendicular to the line

Answer:

4 2 10x y

2 10x y

2 21y x

2 1y x

4 6 12x y 2 3 9x y

32

2y x

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