1. 17

2. Parallel & Perpendicular Lines:
Parallel lines have the same slopes so
find the slope of the given line and the
slope you want for a parallel line will be
the same.
Perpendicular lines have negative reciprocal
slopes. take the slope of the given
line, switch the numerator and denominator
and change the sign for the slope of its
perpendicular line.

3. Practice Problems:

6. EXAMPLE 2
Determine whether lines are parallel or perpendicular
Determine which lines, if any, are parallel or perpendicular.
Line a: y = 5x – 3
Line b:
x + 5y = 2
Line c:
–10y – 2x = 0
SOLUTION
Find the slopes of the lines.
Line a: The equation is in slope-intercept form.
The slope is 5.
Write the equations for lines b and c in slope-intercept form.

7. EXAMPLE 2
Line b:
Determine whether lines are parallel or perpendicular
x + 5y = 2
5y = – x + 2
y=
Line c:
–
1
x +
5
2
5
–10y – 2x = 0
–10y = 2x
y=
–
1
x
5

8. GUIDED PRACTICE
for Example 2
Determine which lines, if any, are parallel or perpendicular.
Line a: 2x + 6y = –3
Line b:
y = 3x – 8
Line c:
–1.5y + 4.5x = 6
ANSWER
parallel: b and c; perpendicular: a and b, a and c

9. Class Work:
4-4
Problems 2,4,6,8,10, change to
perpendicular.
Problems 1,3,5,7,9,11,12; parallel
&
Six Question Review of
Coordinate Unit