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4. Contents Lesson 8-7Writing Linear Equations

5. Lesson 7 Contents Example 1Write Equations From Slope and y-Intercept Example 2Write an Equation From a Graph Example 3Write an Equation to Solve a Problem Example 4Write an Equation Given Two Points Example 5Write an Equation From a Table

6. Example 7-1a Write an equation in slope-intercept form for the line. Slope-intercept form Answer: Replace m with and b with 7.

7. Example 7-1a Write an equation in slope-intercept form for the line. Replace m with 0 and b with –3. Answer: Simplify. Slope-intercept form

8. Example 7-1a Write an equation in slope-intercept form for the line. Slope-intercept form Replace m with 2 and b with 0. Answer: Simplify.

9. Example 7-1b Write an equation in slope-intercept form for each line. a. b. c. Answer:

10. Example 7-2a Write an equation in slope-intercept form for the line graphed. The y -intercept is –4. From (0, –4), you can go up one unit and to the right one unit to another point on the line. So, the slope is 1.

11. Example 7-2a Slope-intercept form Replace m with 1 and b with –4. Answer: Simplify.

12. Example 7-2b Write an equation in slope-intercept form for the line graphed. Answer:

13. Example 7-3a Business The owners of the Good Times Eatery surveyed their customers to find out where they lived. They learned that for each 5-mile radius from their restaurant, 30 fewer people visited them. They had 150 patrons in the area immediately surrounding the diner. Write an equation to show the relationship between miles x and customers y. WordsNumber of customers decreases by 30 for each 5-mile increase in radius. VariablesLet x = miles and let y = customers.

14. Example 7-3a Step 1Find the slope m. EquationsUse. Simplify. decrease of 30 customers increase of 5 miles

15. Example 7-3a Step 2Find the y -intercept b. Slope-intercept form Replace m with –6 and b with 150. Answer: (x, y) = (distance, customers) = (0, b) When the distance is 0 miles, the number of customers is 150. So, the y-intercept is 150. Step 3Write the equation.

16. Example 7-3a Predict the number of customers who lived 20 miles away. Answer:At a distance of 20 miles, the number of customers is 30. Write the equation. Replace x with 20. Simplify.

17. Example 7-3b Weather Attendance at an outdoor sporting event is affected by the temperature outside. When the outside temperature is 0°F, the attendance is 12 people. For every increase in temperature of 20 degrees, the attendance increases by 100 people. a. Write an equation to show the relationship between temperature x and attendance y. b. Predict the attendance if the temperature is 60°F. Answer: 312 Answer:

18. Example 7-4a Write an equation for the line that passes through (7, 0) and (6, 3). Step 1Find the slope m. Definition of slope

19. Example 7-4a Step 2Find the y -intercept b. Use the slope and the coordinates of either point. Slope-intercept form Replace m with –3, x with 7, and y with 0. Simplify.

20. Example 7-4a Step 3Substitute the slope and y -intercept. Replace m with –3 and b with 21. Answer: Slope-intercept form

21. Example 7-4b Write an equation for the line that passes through (4, –2) and (–2, –14). Answer:

22. Example 7-5a Use the table of values to write an equation in slope-intercept form. xy –216 –110 04 1–2 Definition of slope Step 1Find the slope m. Use the coordinates of any two points.

23. Example 7-5a Step 2Find the y -intercept b. Use the slope and the coordinates of either point. Slope-intercept form Replace m with –6, y with 16, and x with –2. Simplify. Step 3Substitute the slope and y -intercept. Answer: Slope-intercept form Replace m with –6 and b with 4.

24. Example 7-5b Use the table of values to write an equation in slope-intercept form. xy –64 –32 3–2 6–4 Answer:

25. End of Lesson 7

26. Pre-Alg.com Explore online information about the information introduced in this chapter. Click on the Connect button to launch your browser and go to the Pre-Algebra Web site. At this site, you will find extra examples for each lesson in the Student Edition of your textbook. When you finish exploring, exit the browser program to return to this presentation. If you experience difficulty connecting to the Web site, manually launch your Web browser and go to www.pre-alg.com/extra_examples.

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