CONFIDENTIAL 1 Transforming Quadratic Functions

CONFIDENTIAL 2 Warm Up Graph each quadratic function. 1) y = 2x ) y = x 2 - 2x - 2 3) y = -3x 2 - x + 6

CONFIDENTIAL 3 Transforming Quadratic Functions The quadratic parent function is f (x) = x 2. The graph of all other quadratic functions are transformations of the graph of f(x) = x 2. For the parent function f (x) = x 2. The axis of symmetry is x = 0, or the y-axis. The vertex is (0, 0). The function has only one zero, x y vertex(0, 0) Axis of symmetry, x=0 f (x) = x 2

CONFIDENTIAL 4 Compare the coefficients in the following functions. f (x) = x 2 g (x) = 1 x 2 2 h (x) = -3x 2 f (x) = 1x 2 + 0x + 0 g (x) = 1 x 2 + 0x h (x) = -3x 2 + 0x + 0 SameDifferent b = 0 c = 0 Value of a ax 2 +bx + c

CONFIDENTIAL 5 Compare the graphs of the same functions. The value of a in a quadratic function determines not only the direction a parabola opens, but also the width of the parabola.

CONFIDENTIAL 6 Width of a Parabola The graph of f (x) = ax 2 is narrower than the graph of f (x) = x 2 if l a l > 1 and wider if l a l < 1. Compare the graphs of g (x) and h (x) with the graph of f (x). l -2 l ? 1 2 > 1 wider 1 ? < 1 4 narrower

CONFIDENTIAL 7 Width of a Parabola Order the functions from narrowest graph to widest. A) f (x) = -2x 2, g (x) = 1 x 2, h (x) = 4x 2 3 Step1: Find l a l for each function. l -2 l = 2 1 = 1 l 4l = Step2: Order the functions. f (x) = -2x 2 g (x) = 1 x 2 3 h (x) = 4x 2 The function with the narrowest graph has the greatest |a|.

CONFIDENTIAL 8 Check: Use a graphing calculator to compare the graphs. h (x) = 4x 2 has the narrowest graph, and g (x) =1 x 2 3 has the widest graph. h (x) = 4x 2 f (x) = -2x 2 g (x) = 1 x 2 3

CONFIDENTIAL 9 B) f (x) = 2x 2, g (x) - 2x 2 Step1: Find l a l for each function. l 2 l = 2 l -2 l = 2 Step2: Order the functions. f (x) = 2x 2 g (x) = -2x 2 Since the absolute values are equal, the graphs are the same width.

CONFIDENTIAL 10 Order the functions from narrowest graph to widest. Now you try! 1) f (x) = -x 2, g (x) = 2 x 2 3 2) f (x) = -4x 2, g (x) = 6x 2, h (x) = 0.2x 2 1) f (x) = -x 2, g (x) = 2 x 2 3 2) g (x) = 6x 2, f (x) = -4x 2, h (x) = 0.2x 2

CONFIDENTIAL 11 Compare the coefficients in the following functions. f (x) = x 2 g (x) = x h (x) = x f (x) = 1x 2 + 0x + 0 g (x) = 1 x 2 + 0x - 4 h (x) = 1x 2 + 0x + 3 SameDifferent a = 1 b = 0 Value of c

CONFIDENTIAL 12 Compare the graphs of the same functions. The value of c makes these graphs look different. The value of c in a quadratic function determines not only the value of the y- intercept but also a vertical translation of the graph of f (x) = ax 2 up or down the y-axis.

CONFIDENTIAL 13 Vertical Translations of a Parabola The graph of the function f (x) = x 2 + c is the graph of f (x) = x 2 translated vertically. If c > 0, the graph of f (x) = x 2 is translated c units up. If c < 0, the graph of f (x) = x 2 is translated c units down.

CONFIDENTIAL 14 Comparing Graphs of Quadratic Functions Compare the graph of each function with the graph of f (x) = x 2. A) g (x) = -1 x Method1: Compare the graphs. The graph of g (x) = (-1/3)x is wider than the graph of f (x) = x 2. The graph of g (x) = (-1/3)x opens downward, and the graph of f (x) = x 2 opens upward. The axis of symmetry is the same. The vertex of f (x) = x 2 is (0, 0). The vertex of g (x) = g (x) = (-1/3)x is translated 2 units up to (0, 2).

CONFIDENTIAL 15 B) g (x) = 2x Method 2: Use the functions. Since l 2 l > l 1 l, the graph of g (x) = 2x is narrower than the graph of f (x) = x 2. Since –b = 0 for both functions, the axis of symmetry is 2a the same. The vertex of f (x) = x 2 is (0, 0). The vertex of g (x) = 2x is translated 3 units down to (0, -3). f (x) = x 2 g (x) = 2x 2 - 3

CONFIDENTIAL 16 Compare the graph of the function with the graph of f (x) = x 2 : Now you try! 1) g (x) = x Since l 1 l = l 1 l, the graph of g (x) = x is equally wider as the graph of f (x) = x 2. Since –b = 0 for both functions, the axis of symmetry is 2a the same. The vertex of f (x) = x 2 is (0, 0). The vertex of g (x) = x is translated 4 units down to (0, -4).

CONFIDENTIAL 17 The quadratic function h (t)=-16t 2 + c can be used to approximate the height h in feet above the ground of a falling object t seconds after it is dropped from a height of c feet. This model is used only to approximate the height of falling objects because it does not account for air resistance, wind, and other real-world factors.

CONFIDENTIAL 18 Two identical water balloons are dropped from different heights as shown in the diagram. a.) Write the two height functions and compare their graphs. b.) Use the graphs to tell when each water balloon reaches the ground. Step 1: Write the height functions. The y-intercept c represents the original height. h1 (t) = -16t Dropped from 64 feet h2 (t) = -16t Dropped from 144 feet 64 feet 144 feet a.)

CONFIDENTIAL 19 Step 2: Use a graphing calculator. Since time and height cannot be negative, set the window for nonnegative values. The graph of h2 is a vertical translation of the graph of h1. Since the balloon in h2 is dropped from 80 feet higher than the one in h1, the y-intercept of h2 is 80 units higher. h1 (t) = -16t h2 (t) = -16t

CONFIDENTIAL 20 b.) Use the graphs to tell when each water balloon reaches the ground. The zeros of each function are when the water balloons reach the ground. The water balloon dropped from 64 feet reaches the ground in 2 seconds. The water balloon dropped from 144 feet reaches the ground in 3 seconds. Check: These answers seem reasonable because the water balloon dropped from a greater height should take longer to reach the ground.

CONFIDENTIAL 21 Now you try! 1) Two tennis balls are dropped, one from a height of 16 feet and the other from a height of 100 feet. a. Write the two height functions and compare their graphs. b. Use the graphs to tell when each tennis ball reaches the ground. h1 (t) = -16t Dropped from 16 feet h2 (t) = -16t Dropped from 100 feet The tennis ball dropped from 16 feet reaches the ground in 1 seconds. The tennis ball dropped from 100 feet reaches the ground in 3 seconds.

CONFIDENTIAL 22 Assessment 1) f (x) = 3x 2, g (x) = 2x 2 2) f (x) = 5x 2, g (x) = -5x 2 Order the functions from narrowest graph to widest. 3) f (x) =2x 2, g ( x) = -2x 2 1) f (x) = 3x 2, g (x) = 2x 2 2) Same width 3) Same width

CONFIDENTIAL 23 6) g (x) = x ) g (x) = 3x ) g (x) = 1 x Compare the graph of the function with the graph of f (x) = x 2 : 5) g (x) is wider than f (x). The vertex of f (x) is (0, 0). The vertex of g (x) is (0, -9). 4) g (x) is narrower than f (x). The vertex of f (x) is (0, 0). The vertex of g (x) is (0, 9). 6) g (x) has same width as f (x). The vertex of f (x) is (0, 0). The vertex of g (x) is (0, 6).

CONFIDENTIAL 24 7) Two baseballs are dropped, one from a height of 16 feet and the other from a height of 256 feet. a. Write the two height functions and compare their graphs. b. Use the graphs to tell when each baseball reaches the ground. h1 (t) = -16t Dropped from 16 feet h2 (t) = -16t Dropped from 256 feet The baseball dropped from 16 feet reaches the ground in 1 second. The baseball dropped from 100 feet reaches the ground in 4 seconds.

CONFIDENTIAL 25 Tell whether each statement is sometimes, always, or never true. 8) The graphs of f (x) = ax 2 and g (x) = -ax 2 have the same width. 9) The function f (x) = ax 2 + c has three zeros. 8) always true

CONFIDENTIAL 26 Let’s review The quadratic parent function is f (x) = x 2. The graph of all other quadratic functions are transformations of the graph of f(x) = x 2. For the parent function f (x) = x 2. The axis of symmetry is x = 0, or the y-axis. The vertex is (0, 0). The function has only one zero, x y vertex(0, 0) Axis of symmetry, x=0 f (x) = x 2

CONFIDENTIAL 27 Compare the coefficients in the following functions. f (x) = x 2 g (x) = 1 x 2 2 h (x) = -3x 2 f (x) = 1x 2 + 0x + 0 g (x) = 1 x 2 + 0x h (x) = -3x 2 + 0x + 0 SameDifferent b = 0 c = 0 Value of a

CONFIDENTIAL 28 Compare the graphs of the same functions. The value of a in a quadratic function determines not only the direction a parabola opens, but also the width of the parabola.

CONFIDENTIAL 29 Width of a Parabola The graph of f (x) = ax 2 is narrower than the graph of f (x) = x 2 if l a l > 1 and wider if l a l < 1. Compare the graphs of g (x) and h (x) with the graph of f (x). l -2 l ? 1 2 > 1 wider 1 ? < 1 4 narrower

CONFIDENTIAL 30 Width of a Parabola Order the functions from narrowest graph to widest. A) f (x) = -2x 2, g (x) = 1 x 2, h (x) = 4x 2 3 Step1: Find l a l for each function. l -2 l = 2 1 = 1 l 4l = Step2: Order the functions. f (x) = -2x 2 g (x) = 1 x 2 3 h (x) = 4x 2 The function with the narrowest graph has the greatest |a|.

CONFIDENTIAL 31 Check: Use a graphing calculator to compare the graphs. h (x) = 4x 2 has the narrowest graph, and g (x) =1 x 2 3 has the widest graph. h (x) = 4x 2 f (x) = -2x 2 g (x) = 1 x 2 3

CONFIDENTIAL 32 Compare the coefficients in the following functions. f (x) = x 2 g (x) = x h (x) = x f (x) = 1x 2 + 0x + 0 g (x) = 1 x 2 + 0x - 4 h (x) = 1x 2 + 0x + 3 SameDifferent a = 1 b = 0 Value of c

CONFIDENTIAL 33 Compare the graphs of the same functions. The value of c makes these graphs look different. The value of c in a quadratic function determines not only the value of the y- intercept but also a vertical translation of the graph of f (x) = ax 2 up or down the y-axis.

CONFIDENTIAL 34 Vertical Translations of a Parabola The graph of the function f (x) = x 2 + c is the graph of f (x) = x 2 translated vertically. If c > 0, the graph of f (x) = x 2 is translated c units up. If c < 0, the graph of f (x) = x 2 is translated c units down.

CONFIDENTIAL 35 Comparing Graphs of Quadratic Functions Compare the graph of each function with the graph of f (x) = x 2. A) g (x) = -1 x Method1: Compare the graphs. The graph of g (x) = (-1/3)x is wider than the graph of f (x) = x 2. The graph of g (x) = (-1/3)x opens downward, and the graph of f (x) = x 2 opens upward. The axis of symmetry is the same. The vertex of f (x) = x 2 is (0, 0). The vertex of g (x) = g (x) = (-1/3)x is translated 2 units up to (0, 2).

CONFIDENTIAL 36 B) g (x) = 2x Method 2: Use the functions. Since l 2 l > l 1 l, the graph of g (x) = 2x is narrower than the graph of f (x) = x 2. Since –b = 0 for both functions, the axis of symmetry is 2a the same. The vertex of f (x) = x 2 is (0, 0). The vertex of g (x) = 2x is translated 3 units down to (0, -3). f (x) = x 2 g (x) = 2x 2 - 3

CONFIDENTIAL 37 You did a great job today!