Lesson 2-2-3-Determine if lines are

parallel, perpendicular, or neither

Parallel/Perpendicular

Comparing slopes of lines can help determine if two lines are parallel, perpendicular, or neither.

Two lines are parallelparallel if they have the same slopes (and different y-

intercepts)

Two lines are perpendicularperpendicular if their slopes are opposite reciprocals

Examples:Determine if the lines are parallel,

perpendicular, or neither.

1) and 4x – y = -1 47

x41

y

Examples:Determine if the lines are parallel,

perpendicular, or neither.

2) the line passing through (1, 6) and (8, -1) and x + y = 2

Examples:3) Write an equation in Slope-Intercept form

of the line passing through the point (5, -3) and perpendicular to the line y = 4x + 1

Examples:4) Write an equation in standard form of the

line passing through (2, 1) and parallel to the line

85

x32

y

Wrap-Up:

How can you use the equations of two non-vertical lines to tell whether the lines are parallel or perpendicular?

Find the slopes and compare:--Same slope – parallel

--Opposite reciprocal slopes - perpendicular

Assignment:

Practice 6-5 worksheet