Writing the Equation of a Line in Slope-Intercept Form

Transcription

1 Writing the Equation of a Line in Slope-Intercept Form Slope-Intercept Form y = mx + b Example 1: Give the equation of the line in slope-intercept form a. With y-intercept (0, 2) and slope -9 b. Passing through (2, 3) with slope -5 c. Passing through (2, 6) and (4, 16) Example 2: Give the equation of the linear function that would generate the following table of values. Use your calculator to check. x f (x)

2 Example 3: Give the equation of the linear function shown below. Example 4: Give the equation of the horizontal line passing through the point (1,3). Example 5: Give the equation of the vertical line passing through the point (1,3). You Try 1. Give the equation of the line passing through the points (1, 7) and (3, -9). 2. Give the equation of the horizontal line passing through the point (5, 11).

3 Parallel and Perpendicular Lines Parallel Lines The slopes of Parallel Lines are Example 1: Give the equation of the line passing through the point (8, 3) that is parallel to the line y = 2x + 3. Perpendicular Lines The slopes of perpendicular lines are If Line 1 and Line 2 are perpendicular to each other, then Slope of line 1 Slope of line Example 2: Give the equation of the line passing through the point (8, 3) that is perpendicular to the line y = 2x + 3.

4 You Try 3. Give the equation of the line passing through the point ( 3, 1) that is parallel to the line y = 8x Give the equation of the line passing through the point ( 3, 1) that is perpendicular to the line y = 8x 5.

5 Applications Slope-Intercept Form Example 1: You have just bought a new television set for $1,400. The value of the television set decreases by $250 per year. Write a formula which represents the value, V, of your television as a function of its age, t, in years. Interpret the slope and intercepts. Example 2: The height of a tree is a function of the amount of time that has passed since it was planted. A tree was 7 feet tall 6 years after it was planted. It was 10 feet tall 15 years after it was planted. Determine a linear function to represent this situation. Interpret the slope and vertical intercept.

6 YOU TRY 5. A new Chevrolet Corvette costs $56,980. The car s value depreciates to $31,870 after four years. a. Determine a linear equation to represent this situation. Clearly indicate what each variable represents. b. Identify the slope and explain its meaning. c. Identify the vertical intercept, and explain its meaning. d. Determine the horizontal intercept, and explain its meaning.

7 General Form: ax + by = c Example 1: Consider the linear equation 3x 5y = 30 a. Write this equation in slope-intercept form b. Identify the slope c. Determine the vertical intercept d. Determine the horizontal intercept.

8 Example 2: Draw an accurate graph of the function 3x + 2y = 16. Slope-Intercept Form: Slope: Vertical Intercept: Horizontal Intercept: Two additional points on the line: YOU TRY 6. Draw an accurate graph of the function 4x y = 7 Slope-Intercept Form: Slope: Vertical Intercept: Horizontal Intercept: Two additional points line:

9 Applications General Form Example 1: Tickets to the circus cost $9 for children and $15 for adults. A total of $5628 was collected in ticket sales on opening night. Let C represent the number of children attending the circus, and let A represent the number of adults attending the circus. a. Write an equation representing the total amount of money collected. b. On opening night, 312 children attended the circus. How many adults were there? YOU TRY 7. Tickets to a college play cost $4 for students and $6 for nonstudents. $2700 was collected at the door in ticket sales. Let S represent the number of student tickets sold, and let N represent the number of nonstudent tickets sold. a. Write an equation representing the total amount of money collected. b. If 342 students attended the play, how many nonstudents were there?

10 Linear Inequalities in Two Variables Example 1: Graph the equation y = 2x 3 The Solution Set Example 2: Which of the ordered pairs below satisfy the equation y 2x 3? (5, 3) (2, 1) (0, 0) Example 3: Which of the ordered pairs below satisfy the inequality y 2x 3? (5, 3) (2, 1) (0, 0) Example 4: Graph the linear inequality y 2x 3.

11 Example 5: Which of the ordered pairs below satisfy the inequality? y 2x 3 (5, 3) (2, 1) (0, 0) Example 6: Graph the linear inequality y 2x 3. You Try 8. Which of the ordered pairs below satisfy the linear inequality y 4 2x? (1,2) (0, 0) (5, 0) 9. Which of the ordered pairs below satisfy the linear inequality y < 4 2x? (1,2) (0, 0) (5, 0)

12 Graphing Linear Inequalities in Two Variables Graphing The Solution Set of a Linear Inequality in Two Variables Step 1: Rewrite the inequality as an equality statement. Step 2: Graph the linear equation. Step 3: Determine if the line should be solid or dotted. If the original inequality statement is either < or >, draw a dotted line. If the original inequality statement is either or, draw a solid line. Step 4: Choose a test point and plug it into the original inequality. If the test point satisfies the inequality, shade in the direction of the test point. If the test point does not satisfy the inequality, shade in the opposite direction of the test point. Example 1: Graph the inequality y < 5 3x Example 2: Graph the inequality 3x 2y 6

13 Example 3: Graph the inequality y 2x 10. Graph the inequality y > 2x 1 You Try