1. Activating Prior Knowledge-
On your warm up page, draw and label a set of parallel lines.
On your warm up page, draw and label a set of perpendicular lines.
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2. identify parallel and perpendicular lines.
Learning Objective
Today, we will
identify parallel and perpendicular lines.
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3. Concept Development – Notes #1 & 2
(No Notes) These two lines are parallel.
1. Parallel lines are lines in the same plane that have no points in common.
2. In other words, they do not intersect.
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4. Concept Development – Notes #3
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5. Concept Development - CFU
Draw a line through point (1,1) with a slope of 2.
Draw a line that is parallel to this line.
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6. What do I know about the slopes of parallel lines?
Concept Development -
How would I identify which lines are parallel?
y = − 𝟏 𝟑 x + 2
y = 3x + 1
y = -3x+1
y = 3x
What do I know about the slopes of parallel lines?
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7. What do I need to do first to identify the slope?
Concept Development -
How would I identify which lines are parallel?
2x + y = 2
y = -2x+1
6x + 3y = 9
y + 4x = 1
What do I need to do first to identify the slope?
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8. Skill Development/Guided Practice – Notes #4
Identify which lines are parallel.
y = 2x + 2; y = 2x + 1; y = –4; x = 1
y = 2x + 2
The lines described by
y = 2x + 2 and y = 2x + 1 represent parallel lines. They each have slope 2.
y = 2x + 1
Equations x = 1 and
y = –4 are not parallel.
y = –4
x = 1
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9. Skill Development/Guided Practice – Notes #5
Identify which lines are parallel.
Write all equations in slope-intercept form to determine the slope.
y = 2x – 3 slope-intercept form  
slope-intercept form
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10. Skill Development/Guided Practice – Cont. Notes #5
Identify which lines are parallel.
Write all equations in slope-intercept form to determine the slope.
2x + 3y = 8
y + 1 = 3(x – 3)
–2x – 2x
y + 1 = 3x – 9
3y = –2x + 8
– – 1
y = 3x – 10
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11. Skill Development/Guided Practice – Cont. Notes #5
The lines described by y = 2x – 3
and y + 1 = 3(x – 3) are not parallel with any of the lines.
The lines described by
and represent parallel lines. They each have the slope .
y = 2x – 3
y + 1 = 3(x – 3)
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12. y = 2x + 9 Concept Development - CFU
Find the slope of a line parallel to each given line.
y = 2x + 9
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13. y = -3x Concept Development - CFU
Find the slope of a line parallel to each given line.
y = -3x
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14. 2x + y = 4 Concept Development - CFU
Find the slope of a line parallel to each given line.
2x + y = 4
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15. 3x + y = 1 Concept Development - CFU
Find the slope of a line parallel to each given line.
3x + y = 1
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16. Concept Development – Notes #6
Perpendicular lines are lines that intersect to form right angles (90°).
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17. Concept Development - Whiteboard
Graph the line y = 2x + 3.
Write an equation that is perpendicular to y = 2x + 3.
Graph that line.
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18. Concept Development - Whiteboard
How would I identify which lines are perpendicular?
y = − 𝟏 𝟑 x + 2
y = 3x + 1
y = -3x+1
y = 3x
What do I know about the slopes of perpendicular lines?
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19. Skill Development/Guided Practice – Notes #7
Identify which lines are perpendicular: y = 3; x = –2; y = 3x;
The graph given by y = 3 is a horizontal line, and the graph given by x = –2 is a vertical line. These lines are perpendicular.
x = –2
y = 3
The slope of the line given by y = 3x is 3. The slope of the line described by
is .
y =3x
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20. Skill Development/Guided Practice – Cont. Notes #7
Identify which lines are perpendicular: y = 3; x = –2; y = 3x;
x = –2
y = 3
These lines are perpendicular because the product of their slopes is –1.
y =3x
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21. Closure – Paper CFU 1. What did we learn today?
2. Why is this important to you?
3. Two parallel lines will have slopes that are ________?
4. Write two linear equations in slope-intercept form that are parallel.
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