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  1. 1-8 Introduction to Functions Holt Algebra 1 Warm Up Lesson Presentation Lesson Quiz

  2. - - - - - - 6 5 4 3 2 1 0 1 2 3 4 5 6 Warm Up Add. 1. Draw and label a number line. Then plot the points –2, 0, and 4. • • • Evaluate each expression for the given value of x. 2. 2x + 1 for x = 3 7 1 4 1 – x + 3 for x = 8 3. 4 4. |x + 6| for x = –10

  3. Objectives Graph ordered pairs in the coordinate plane. Graph functions from ordered pairs.

  4. Vocabulary coordinate plane axes origin x-axis y-axis ordered pair x-coordinate y-coordinate quadrant input output

  5. The coordinate plane is formed by the intersection of two perpendicular number lines called axes. The point of intersection, called the origin, is at 0 on each number line. The horizontal number line is called the x-axis, and the vertical number line is called the y-axis.

  6. Reading Math The x-coordinate tells how many units to move left or right from the origin. The y-coordinate tells how many units to move up or down. Points on the coordinate plane are described using ordered pairs. An ordered pair consists of an x-coordinate and a y-coordinate and is written (x, y). Points are often named by a capital letter.

  7. U(0, –5) • Example 1: Graphing Points in the Coordinate Plane Graph each point. A. T(–4, 4) Start at the origin. T(–4, 4) • Move 4 units left and 4 units up. B. U(0, –5) Start at the origin. Move 5 units down. • C. V (–2, –3) V(–2, −3) Start at the origin. Move 2 units left and 3 units down.

  8. Check It Out! Example 1 Graph each point. A. R(2, –3) Start at the origin. T(–2,6) Move 2 units right and 3 units down. S(0,2) B. S(0, 2) Start at the origin. Move 2 units up. C. T(–2, 6) • R(2, –3) Start at the origin. Move 2 units left and 6 units up.

  9. Look at the graph at the top of this lesson. The axes divide the coordinate plane into four quadrants. Points that lie on an axis are not in any quadrant.

  10. •F •E •G •H Example 2: Locating Points in the Coordinate Plane Name the quadrant in which each point lies. y A. E Quadrant ll B. F no quadrant (y-axis) x C.G Quadrant l D.H Quadrant lll

  11. Check It Out! Example 2 Name the quadrant in which each point lies. y A. T •U •W no quadrant (y-axis) •T B. U Quadrant l x C.V Quadrant lll •V D.W Quadrant ll

  12. An equation that contains two variables can be used as a rule to generate ordered pairs. When you substitute a value for x, you generate a value for y. The value substituted for x is called the input, and the value generated for y is called the output. Output Input y= 10x + 5 In a function, the value of y (the output) is determined by the value of x (the input). All of the equations in this lesson represent functions.

  13. Engraver’s fee is $10 plus word $2 for each y 10 x = + 2 · Example 3: Art Application An engraver charges a setup fee of $10 plus $2 for every word engraved. Write a rule for the engraver’s fee. Write ordered pairs for the engraver’s fee when there are 5, 10, 15, and 20 words engraved. Let y represent the engraver’s fee and x represent the number of words engraved. y = 10 + 2x

  14. Writing Math The engraver’s fee is determined by the number of words in the engraving. So the number of words is the input and the engraver’s fee is the output.

  15. Example 3 Continued 5 y = 10 + 2(5) 20 (5, 20) 10 30 (10, 30) y = 10 + 2(10) y = 10 + 2(15) 15 (15, 40) 40 20 50 y = 10 + 2(20) (20, 50)

  16. Artist’s fee is $10 plus person $20 for each y 10 x = + 20 · Check It Out! Example 4 What if…? The caricature artist increased his fees. He now charges a $10 set up fee plus $20 for each person in the picture. Write a rule for the artist’s new fee. Find the artist’s fee when there are 1, 2, 3 and 4 people in the picture. Let y represent the artist’s fee and x represent the number of people in the picture. y = 10 + 20x

  17. Check It Out! Example 4 Continued 1 y = 10 + 20(1) 30 (1, 30) 2 50 (2, 50) y = 10 + 20(2) y = 10 + 20(3) 3 (3, 70) 70 4 90 y = 10 + 20(4) (4, 90)

  18. When you graph ordered pairs generated by a function, they may create a pattern.

  19. • • • • Example 4A: Generating and Graphing Ordered Pairs Generate ordered pairs for the function using the given values for x. Graph the ordered pairs and describe the pattern. y = 2x + 1; x = –2, –1, 0, 1, 2 (–2, –3) –2 2(–2)+ 1 = –3 2(–1)+ 1 = –1 (–1, –1) –1 2(0)+ 1 = 1 (0, 1) 0 2(1) + 1 = 3 1 (1, 3) 2(2) + 1 = 5 (2, 5) 2 The points form a line.

  20. Example 4B: Generating and Graphing Ordered Pairs y = x2– 3; x = –2, –1, 0, 1, 2 (–2, 1) –2 (–2)2– 3 = 1 (–1)2– 3 = –2 –1 (–1, –2) (0)2– 3 = –3 (0, –3) 0 (1)2– 3 = –2 1 (1, –2) (2)2– 3 = 1 (2, 1) 2 The points form a U shape.

  21. Example 4C: Generating and Graphing Ordered Pairs y = |x –2|; x = 0, 1, 2, 3, 4 0 (0, 2) |0– 2| = 2 |1– 2| = 1 1 (1, 1) |2– 2| = 0 (2, 0) 2 |3– 2| = 1 3 (3, 1) (4, 2) 4 |4– 2| = 2 The points form a V shape.

  22. 1 2 Check It Out! Example 4a y = x – 4; x = –4, –2, 0, 2, 4 (–4, –6) –4 –2 – 4 = –6 –2 –1 – 4 = –5 (–2, –5) 0 – 4 = –4 (0, –4) 0 1 – 4 = –3 2 (2, –3) 4 2 – 4 = –2 (4, –2) The points form a line.

  23. Check It Out! Example 4b y = 3x2 + 3; x = –3, –1, 0, 1, 3 (–3, 30) –3 3(–3)2+ 3 = 30 3(–1)2+ 3 = 6 –1 (–1, 6) 3(0)2+ 3 = 3 (0, 3) 0 3(1)2+ 3 = 6 1 (1, 6) 3(3)2+ 3 = 30 (3, 30) 3 The points form a U shape.

  24. Check It Out! Example 4c y = |x– 2|; x = 0, 1, 2, 3, 4 0 (0, 2) |0– 2| = 2 |1– 2| = 1 1 (1, 1) |2– 2| = 0 (2, 0) 2 |3– 2| = 1 3 (3, 1) (4, 2) 4 |4– 2| = 2 The points form a V shape.

  25. Lesson Quiz: Part 1 Graph each point. Name the quadrant in which each point lies. 1. (2, 0) None 2. (–3, –4) lll • 3. (1, –1) lV • • 4. (–5, 4) ll •

  26. Lesson Quiz: Part 2 5. A cable company charges $50 to set up a movie channel and $3.00 per movie watched. Write a rule for the company’s fee. Write ordered pairs for the fee when a person watches 1, 2, 3, or 4 movies. y = 50 + 3x; (1, 53), (2, 56), (3, 59), (4, 62)

  27. • • • • Lesson Quiz: Part 3 6. Generate ordered pairs for y = x² –5 using x = –2, –1, 0, 1, and 2. Graph the ordered pairs, and describe the pattern. (–2, –1) (–1, –4) (0, –5) (1, –4) (2, –1) The pattern is U-shaped.