8.1 Writing Equations of Parallel & Perpendicular Lines

Writing Equations of Parallel Lines

How can we determine if lines are parallel?

Parallel and Slopes

• Two lines in the same plane that never intersect.

• Two lines are parallel if and only if they have the same slope.

Identifying parallel lines

• Find the slope of each line

• When a graph is present we can use rise/run

• Use ll symbol to write which lines are parallel

Multiple Choice

Determine which lines are parallel

• a ll b

• b ll c

• c ll a

Identifying Parallel Lines

When there is no graph present, use the slope formula y2-y1/ x2-x1.

Then compare slopes

Multiple Choice

Determine which lines are parallel.

• a ll b

• b ll c

• a ll c

Multiple Choice

Determine which lines are parallel.

• a ll b

• b ll c

• a ll c

• None

Multiple Choice

Write the equation of a line that is parallel to  $$y=-x+12$$  and goes through the point  $$\left(3,\ -10\right).$$  

• $$y=-x-7$$  

• $$y=-x-10$$  

• $$y=-x-13$$  

• $$y=-x+3$$  

Multiple Choice

Write the equation of a line that is parallel to  $$y=7x+2$$  and goes through the point  $$\left(-2,\ -9\right).$$

• $$y=7x-23$$  

• $$y=7x+5$$  

• $$y=7x-9$$  

• $$y=7x-2$$  

Multiple Choice

Write the equation of a line that is parallel to the given line and goes through  $$\left(-7,\ 1\right).$$  

• $$y=2x-3$$  

• $$y=2x-13$$  

• $$y=2x+15$$  

• $$y=2x+1$$  

Multiple Choice

Write the equation of a line that is parallel to the given line and goes through  $$\left(0,\ -14\right).$$  

• $$y=-3x-14$$  

• $$y=3x-14$$  

• $$y=-3x+2$$  

• $$y=3x+2$$  

Multiple Choice

What is the rate of change for the table?

• $$-\frac{5}{2}$$  

• $$-\frac{2}{5}$$  

• $$\frac{5}{2}$$  

• $$-\frac{11}{2}$$  

A.2.F Writing Equations of Perpendicular Lines

Multiple Choice

Slopes of perpendicular lines are...

• opposite reciprocals.
• opposites.
• identical.
• always 7.

Multiple Choice

What slope is perpendicular to:  
m = 5/8

• -5/8
• 5/8
• -8/5
• 8/5

Multiple Choice

What slope is perpendicular to:  
m = 3

• -3
• -1/3
• 1/3
• 3

Match

Match the following opposite reciprocal

• -2/3

• 5/4

• 15/4

• -7/5

3/2

-4/5

-4/15

5/7

• 3/2

• -4/5

• -4/15

• 5/7

Match

Match the following

Parallel lines

Perpendicular lines

Intersecting lines

• Parallel lines

• Perpendicular lines

• Intersecting lines

Multiple Choice

A line is perpendicular to    y = 2x - 7.
What is the slope of this line? 

• -2
• 1/2
• -1/2
• 2

Multiple Choice

y = -2/3x + 2
y = 3/2x + 9
These lines are...

• Parallel
• Perpendicular
• Neither

Multiple Choice

y = 5/7x +2
y = 5/7x - 30
These lines are...

• Parallel
• Perpendicular
• Neither

Multiple Choice

Are the two linear equations parallel, perpendicular, or neither?

• Parallel

• Perpendicular

• Neither

Multiple Choice

What is the equation of a line that passes through the point (0, -4) and is perpendicular to

$$y=-\frac{3}{2}x+1$$  

• $$y=\frac{2}{3}x-4$$  

• $$y=\frac{2}{3}x+4$$  

• $$y=-\frac{2}{3}x-4$$  

• $$y=-\frac{2}{3}x+4$$