U4L9 Parallel and Perpendicular lesson

U4L9 Parallel and Perpendicular lesson

How do we know when two lines are parallel?

• Graphically when the lines never touch

• Algebraically when the slopes are the same

Multiple Choice

Are the lines shown parallel, perpendicular, or neither?

• parallel

• perpendicular

• neither

• not enough information

Parallel?

Yes, because the slopes are both 2

When are two lines perpendicular?

• When the intersect at a right angle

• When their slopes are opposite reciprocals

Multiple Choice

Are the two lines perpendicular?

 $y=2x+1$  and  $y=\frac{1}{2}x-1$  

• perpendicular

• not perpendicular

Multiple Choice

Are the two lines perpendicular?

 $y=2x+1$  and  $y=-2x-1$  

• perpendicular

• not perpendicular

Multiple Choice

Are the two lines perpendicular?

 $y=2x+1$  and  $y=-\frac{1}{2}x-1$  

• perpendicular

• not perpendicular

Open Ended

Create a pair of slopes that are negative reciprocals.