1. 2.4: Writing Equations of Lines
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18)
Perpendicular
19)
Neither
20)
Parallel
21)
22)
23)
24)
$6/hr
25)
13 mi/gallon
26)
4 ft/sec
27)
2 m/sec
29) 2
31)
1/6
33)
-3/2
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2.4: Writing Equations of Lines

2. 2.4: Writing Equations of Lines
Page 93 3)
Slope is 3 times the P.F. 7)
Slope is 2x and the P.F. and down 1
11)
15)
19)
23) C
24)
X-int.: (4, 0), Y-int.: (0, –4)
25)
X-int.: (–15, 0), Y-int.: (0, –3)
26)
X-int.: (–4, 0), Y-int.: (0, 3)
27)
X-int.: (5, 0), Y-int.: (0, –10)
28)
X-int.: (5, 0), Y-int.: (0, –4)
29)
X-int.: (6, 0), Y-int.: (0, –4.5)
30)
45)
49)
53)
57)
Slope: -A/B; Y-int.: (0, C/B)
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2.4: Writing Equations of Lines

3. 2.4: Writing Equations of Lines
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2.4: Writing Equations of Lines

4. Writing Equations of Lines
Section 2.4
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2.4: Writing Equations of Lines

5. 2.4: Writing Equations of Lines
Slope Equation:
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2.4: Writing Equations of Lines

6. 2.4: Writing Equations of Lines
Recall
Slope
Y-intercept
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2.4: Writing Equations of Lines

7. 2.4: Writing Equations of Lines
Example 1
Graph y = –2x + 3
y = mx + b
y = mx + 3
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2.4: Writing Equations of Lines

8. 2.4: Writing Equations of Lines
Example 1
Graph y = –2x + 3
y = mx + b
y = mx + 3
y = –2x + 3
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2.4: Writing Equations of Lines

9. 2.4: Writing Equations of Lines
Example 2
Graph y = –1/2x – 5/2
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2.4: Writing Equations of Lines

10. 2.4: Writing Equations of Lines
Example 3
Graph y = 4, identify slope and y-intercept
Slope: Zero
Y-intercept: (0, 4)
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2.4: Writing Equations of Lines

11. Your Turn Graph x = –1, identify slope and y-intercept
Slope: No Slope or Undefined
Y-intercept: None
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2.4: Writing Equations of Lines

12. 2.4: Writing Equations of Lines
Point-Slope Equation
X1 is the x-coordinate
Y1 is the y-coordinate
Slope
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2.4: Writing Equations of Lines

13. 2.4: Writing Equations of Lines
Example 4
Given below:
Write an equation in Point-Slope Form.
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2.4: Writing Equations of Lines

14. 2.4: Writing Equations of Lines
Example 4
What are the two points given?
(4, 0) and (0, –2)
What is the slope of this equation?
m = 1/2
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2.4: Writing Equations of Lines

15. 2.4: Writing Equations of Lines
Example 4
If a point and a slope is given, use the point-slope formula
y – y1 = m (x – x1)
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2.4: Writing Equations of Lines

16. 2.4: Writing Equations of Lines
Example 4
y – y1 = m (x – x1)
y – (–2) = ½ (x – 0)
y + 2 = 1/2x
y = 1/2x – 2
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2.4: Writing Equations of Lines

17. 2.4: Writing Equations of Lines
Example 5
Given point (4, –2) and the graph below, write the equation
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2.4: Writing Equations of Lines

18. 2.4: Writing Equations of Lines
Example 5
What is a point given?
(4, –2) and (0, 3)
What is the slope of this equation?
m= –5/4
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2.4: Writing Equations of Lines

19. 2.4: Writing Equations of Lines
Example 5
y – y1 = m (x – x1)
y – (3) = –5/4(x – 0)
y - 3 = –5/4x
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2.4: Writing Equations of Lines

20. 2.4: Writing Equations of Lines
Example 6
Given point (–1, –5) and the slope of ¾, write an equation in Point-Slope Form
y – y1 = m (x – x1)
y – (–5) = 3/4 (x – (–1))
y + 5 = ¾(x + 1)
y = 3/4x – 17/4
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2.4: Writing Equations of Lines

21. 2.4: Writing Equations of Lines
Your Turn
If given point (–1, –4) and the slope of 7/2, draw the graph and write the equation in Point-Slope Form
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2.4: Writing Equations of Lines

22. 2.4: Writing Equations of Lines
Example 7
Determine an equation of the line containing the points (2, 3) and (–4, 5)
What equations will you need?
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2.4: Writing Equations of Lines

23. 2.4: Writing Equations of Lines
Example 7
Determine an equation of the line containing the points (2, 3) and (–4, 5).
What equations will you need?
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2.4: Writing Equations of Lines

24. 2.4: Writing Equations of Lines
Example 8
Determine an equation of the line containing the points (2, 5) and (–3, 4).
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2.4: Writing Equations of Lines

25. 2.4: Writing Equations of Lines
Your Turn
Determine an equation of the line containing the points (3, 12) and (6, 27).
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2.4: Writing Equations of Lines

26. Given Point and Equation
Rewrite the equation in Y-intercept form
Apply the appropriate slope
Plug in points using Point-Slope form
Simplify
Remember:
PARALLEL: SAME SLOPES
PERPENDICULAR: OPPOSITE SIGN RECIPROCAL
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2.4: Writing Equations of Lines

27. 2.4: Writing Equations of Lines
Review
Line 1 contains points of (0, 5) and (2, 0)
Line 2 contains points of (5, 0) and (0, –2)
Is it parallel, perpendicular, or neither?
PERPENDICULAR
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2.4: Writing Equations of Lines

28. 2.4: Writing Equations of Lines
Example 9
Write an equation of the line that passes through (–2, 3) and is (a) parallel and (b) perpendicular to the line y = –4x Write answers in Point-Slope form.
Parallel
Perpendicular
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2.4: Writing Equations of Lines 28

29. 2.4: Writing Equations of Lines
Example 10
Write an equation of the line in slope-intercept form which is parallel to the line 2x + y = 10 and containing the point (–1, 3).
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2.4: Writing Equations of Lines

30. 2.4: Writing Equations of Lines
Your Turn
Write an equation of the line in slope-intercept form which is perpendicular to 4y – x = 20 and containing the point (2, –3).
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2.4: Writing Equations of Lines

31. Assignment:
Pg 101:
3-39 odd, 46
9-17: Leave your answers in point-slope form
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2-4: Writing Linear Functions
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2.4: Writing Equations of Lines 31