1. Warm Up
Tuesday 11/9/10 We will graph linear equations using intercepts.
Simplify each expression:

2. Warm Up
Wednesday 11/10/10 We will graph linear equations using intercepts.
Solve each equation:

3. Today’s Objective
To be able to find the x and y intercepts of an equation and use them to draw a quick graph.

4. The intercepts are where the line crosses the axis.
y-Intercept = 6 y
x-Intercept = 2 x

5. Intercepts: Find the x and y intercepts then graph the line
y intercept x = 0
Substitute 0 in for x then solve for y
x intercept y = 0
Substitute 0 in for y then solve for x

6. Graph of equation
Next graph the x intercept x = -5 at the point (-5,0)
First graph the y intercept y = -4 at the point (0,-4)
Finally connect the points to form a line

7. Intercepts: Find the x and y intercepts then graph the line
y intercept x = 0
Substitute 0 in for x then solve for y
x intercept y = 0
Substitute 0 in for y then solve for x

8. Graph of equation
Next graph the x intercept x = 12 at the point (12,0) (change scale count by 2s)
First graph the y intercept y = -8 at the point (0,-8)
Finally connect the points to form a line

9. Compare the 2 graphs

10. Find the intercepts and graph
3x + 4y = 12

11. Finding the x-intercept
3x + 4y = 12
3x + 4(0) = 12
3x + 0 = 12
3x = 12
x = 4

12. Finding the y-intercept
3x + 4y = 12
3(0) + 4y = 12
0 + 4y = 12
4y = 12
y = 3

13. The graph of 3x + 4y = 12 y
y-intercept = 3
x-intercept = 4 x

14. Find the intercepts and graph
y = 4x - 4
You try this one.

15. Finding the x-intercept
y = 4x - 4
0 = 4x - 4
0 + 4 = 4x
4 = 4x
1 = x

16. Finding the y-intercept
y = 4x - 4
y = 4(0) - 4
y = -4

17. The graph of y = 4x - 4 y
x-intercept = 1 x
y-intercept = -4

18. What is the x-intercept of 3x – 4y = 24?
(3, 0)
(8, 0)
(0, -4)
(0, -6) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

19. What is the y-intercept of -x + 2y = 8?
(-1, 0)
(-8, 0)
(0, 2)
(0, 4) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

20. What is the y-intercept of x = 3?
(3, 0)
(-3, 0)
(0, 3)
None 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

21. Word Problem
You make and sell decorative bows. You sell small bows for $3 and large bows for $5. You want to earn $60 per week. This situation can be modeled by 3x + 5y = 60 where x is the number of small bows and y is the number of large bows.
Find the intercepts of the graph.
Graph the equation
Give 3 possible solutions

22. Finding the y-intercept
3x + 5y = 60
3(0) + 5y = 60
5y = 60
y = 12
(0, 12)

23. Finding the x-intercept
3x + 5y = 60
3x + 5(0) = 60
3x = 60
x = 20
(20, 0)

24. Graph of the Equation
Large Bows Sold
Small Bows Sold

25. Three Possible Solutions
0 small, 12 large
Large Bows Sold
10 small, 6 large
20 small, 0 large
Small Bows Sold

26. Word Problem Your debt d (in dollars) is given by the function:
You borrow $1800 from your parents.
To repay your debt, you give them $150 per month.
Your debt d (in dollars) is given by the function:
d = 150t where t represents time in (months)
Find the intercepts of the graph of the function and state what they represent.
Graph the equation and identify its domain and range.

27. Finding the t-intercept
d = 150t
Set d = = 150t – 1800
1800 = 150t
12 = t
In 12 months the debt = 0

28. Finding the d-intercept
d = 150t
Set t = d = 150(0)
d =
The debt is -$1800 when time is 0.

29. Graph the function d = 150t -1800
Put time (t) on the x axis
Put debt (d) on the y axis

30. Graph of the function d = 150t -1800
time (t) in months
(12, 0)
debt (d) in dollars

31. Identify the domain and range 
time (t) in months
Range:
debt (d) in dollars

32. Guided Practice
Pgs. 225 – 228
Examples 1 – 5