Parallel and Perpendicular Lines

1
Parallel and Perpendicular Lines

• 6-5

2
Parallel Lines

• Same slope different y-intercepts
• Put lines in slope intercept form to tell if they
  are parallel.
• Example
• y1/2x 4
• y1/2x - 6

3
Find the slope of the line parallel to the line
given.

• y3x 1
• y 1/3x 9
• y 5

4
Are the following lines parallel?

• y -1/3x 3 and 2x 6y 12
• -6x 8y 24 and y 3/4x -7

5
Perpendicular Lines

• Lines that cross at right angles.
• Slope of line 1 times the slope of line 2 -1
• OR one slope is the negative recipricol of the
  other.

6
Example of perpendicular lines

• y 3x 2 and y -1/3x -5

7
Find and equation of a line through (0,-2) and
perpendicular to y5x 3

• Step 1 Identify the negative recipricol slope
• Step 2 Use neg recipricol slope and point in
  point slope form.
• Step 3 Put the equation into slope-intercept
  form.

8
Example

• Find an equation of a line perpendicular to
• y3/4x 1 and through the point (1,8).

9
Are the following lines parallel, perpendicular
or neither?

• y-1/4x 1 and y4x 2
• y-1/2x 4 and x 2y -5
• 2x y 7 and y -3x 1

10
Home Work

• Pg. 307 2-42 even