1. 3.4 Equations of Lines Then: You found the slopes of lines. Now: 1. Write an equation of a line given information about the graph. 2. Solve problems by writing equations.

2. Review : Swim Lessons The graph models the total cost of joining a gym and taking swim lessons. Slope of the graph is y = 15x + 20 1. What is the slope of this equation? 2. What is the y-intercept? 3. What is the cost to join? Cost for 5 lessons?

3. Vocabulary: 1. Slope- intercept form: y = mx + b where m is the slope of the line and b is the y- intercept 2. Point-slope form: y – y 1 = m(x – x 1 ) where (x 1, y 1 ) is any point on the line and m is the slope of the line. http://mathsongs.com/bookpix/cd7a.jpg

4. Example 1: Write an equation in slope-intercept form of the line having a slope of 4 and y-intercept of 3. Then graph the line. Equation: http://www.jamesrahn.com/graph%20paper/IMAGES/graph_16.gif

5. Example 2: Write an equation in point-slope form of the line having a slope of 5 and contains (3, -2). Then graph the line. Equation:

6. Example 3: Write an equation of the line through each pair of points in slope-intercept form. (0,-1) and (4,4) 1. Find the slope - 2. Use Point slope form to find equation-

7. Horizontal and Vertical Line Equations 1. Equation of horizontal line: y = b, where b is the y-intercept of the line y = ________ 2. Equation of vertical line: x = a, where a is the x-intercept of the line. x = _________ https://share.ehs.uen.org/sites/default/files/images/grid%20of%205%27s.png

8. Example 4: Write an equation of the line through each pair of points in slope-intercept form. a. (-1, -4), (3,-4) Slope = b. (-3, -2), (-3, 4) Slope =

9. 3.4 Assignment Day 1: p. 202-203 #14-32 Evens, 42 a-c graph 14, 20, 22 graph #42 on large paper with x and y axis

10. Example 5: Write an equation in slope- intercept form for the line described.

12. Example 6: Rental Costs An apartment complex charges $525 per month plus a $750 annual maintenance fee. a. Write an equation to represent the total first year’s cost A for r months of rent.

13. Example 6 cont. b. Compare this rental cost to a complex which charges $200 annual maintenance fee but $600 per month for rent. If a person expects to stay in an apartment for one year, which complex offers the better rate?

14. 3.4 Assignment: Day 2: pages 203-205 #37-40, 43-53,55, 60-63, 70-73