Algebra 1: Parallel & Perpendicular Lines

Given y = 7x - 4 what is this line's slope?

• 1

• 7

• -4

Answer explanation

This is slope-intercept form.

y = mx + b where you can easily read the slope (m).

Given y + 7 = -4(x - 5) what is this line's slope?

• -7

• 5

• -4

Answer explanation

This is point-slope form where you can easily read the slope (m).

y - y₁ = m(x - x₁)

Given x + 7y = - 4 what is this line's slope?

• 1

• 7

• -1/7

Answer explanation

This is standard form which you cannot read slope from.

We must solve this into slope-intercept form (y=mx+b) to help us.

x+7y = -4

7y = -x - 4

y = (-1/7)x - 4/7

Parallel Lines

• never intersect

• intersect at a 90^o angle

• can be any two lines

Answer explanation

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CCSS.HSG.CO.A.1

Perpendicular Lines

• never intersect

• intersect at a 90^o angle

• can be any two lines

Answer explanation

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CCSS.4.G.A.1

CCSS.HSG.CO.A.1

The slopes of Parallel Lines must be

• the same

• opposite reciprocals

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CCSS.4.G.A.1

CCSS.HSG.CO.A.1

The slopes of Perpendicular Lines must be

• the same

• opposite reciprocals

Which pair of slopes would be identified as Parallel?

• 2 and 1/2

• 2 and -2

• 2 and 2

• 2 and -1/2

Answer explanation

Parallel slopes are the SAME

Which pair of slopes would be identified as Perpendicular?

• 2 and 1/2

• 2 and -2

• 2 and 2

• 2 and -1/2

Answer explanation

Perpendicular slopes are the OPPOSITE RECIPROCALS meaning change the sign & flip.

Which line is PARALLEL 

to   y - 3 = -2(x + 4)?

•  $y=2x-9$ 

•  $y=-2x-9$ 

•  $y=-\frac{1}{2}x-9$ 

•  $y=\frac{1}{2}x-9$ 

Answer explanation

the old line is in point-slope form so we can see the slope is -2

A line parallel to the old line must have a -2 slope!

Tags

CCSS.4.G.A.1

CCSS.HSG.CO.A.1