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**Give the coordinate of the vertex of each function.**

Warm Up Give the coordinate of the vertex of each function. 1. f(x) = (x – 2)2 + 3 (2, 3) 2. f(x) = 2(x + 1)2 – 4 (–1,–4) 3. Give the domain and range of the following function. {(–2, 4), (0, 6), (2, 8), (4, 10)} D:{–2, 0, 2, 4}; R:{4, 6, 8, 10}

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**Objectives Define, identify, and graph quadratic functions.**

Identify and use maximums and minimums of quadratic functions to solve problems.

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**This shows that parabolas are symmetric curves**

This shows that parabolas are symmetric curves. The axis of symmetry is the line through the vertex of a parabola that divides the parabola into two congruent halves.

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**Example 1: Identifying the Axis of Symmetry**

Identify the axis of symmetry for the graph of . Rewrite the function to find the value of h. Because h = –5, the axis of symmetry is the vertical line x = –5.

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Check It Out! Example1 Identify the axis of symmetry for the graph of Rewrite the function to find the value of h. f(x) = [x - (3)]2 + 1 Because h = 3, the axis of symmetry is the vertical line x = 3.

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**Another useful form of writing quadratic functions is the standard form.**

The standard form of a quadratic function is f(x)= ax2 + bx + c, where a ≠ 0.

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**These properties can be generalized to help you graph quadratic functions.**

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**Example 2A: Graphing Quadratic Functions in Standard Form**

Consider the function f(x) = 2x2 – 4x + 5. a. Determine whether the graph opens upward or downward. b. Find the axis of symmetry. c. Find the vertex. d. Find the y-intercept.

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**Example 2A: Graphing Quadratic Functions in Standard Form**

Consider the function f(x) = 2x2 – 4x + 5. e. Graph the function.

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**Example 2B: Graphing Quadratic Functions in Standard Form**

Consider the function f(x) = –x2 – 2x + 3. a. Determine whether the graph opens upward or downward. b. Find the axis of symmetry. c. Find the vertex. d. Find the y-intercept.

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**Example 2B: Graphing Quadratic Functions in Standard Form**

Consider the function f(x) = –x2 – 2x + 3. e. Graph the function.

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**The minimum (or maximum) value is the y-value at the vertex**

The minimum (or maximum) value is the y-value at the vertex. It is not the ordered pair that represents the vertex. Caution!

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**Example 3: Finding Minimum or Maximum Values**

Find the minimum or maximum value of f(x) = –3x2 + 2x – 4. Then state the domain and range of the function. Step 1 Determine whether the function has minimum or maximum value. Step 2 Find the x-value of the vertex. Step 3 Then find the y-value of the vertex.

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**Check It Out! Example 3a Continued**

Graph f(x)=x2 – 6x + 3 on a graphing calculator. The graph and table support the answer.

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Example 4 The highway mileage m in miles per gallon for a compact car is approximately by m(s) = –0.025s s – 30, where s is the speed in miles per hour. What is the maximum mileage for this compact car to the nearest tenth of a mile per gallon? What speed results in this mileage?

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Example 4 Continued The maximum value will be at the vertex (s, m(s)). Step 1 Find the s-value of the vertex using a = –0.025 and b = 2.45. ( ) 2.45 0.02 2 5 49 b s a - = - =

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**The maximum mileage is 30 mi/gal at 49 mi/h.**

Example 4 Continued Step 2 Substitute this s-value into m to find the corresponding maximum, m(s). m(s) = –0.025s s – 30 Substitute 49 for r. m(49) = –0.025(49) (49) – 30 m(49) ≈ 30 Use a calculator. The maximum mileage is 30 mi/gal at 49 mi/h.

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Example 4 Continued Check Graph the function on a graphing calculator. Use the MAXIMUM feature under the CALCULATE menu to approximate the MAXIMUM. The graph supports the answer.

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Lesson Quiz: Part I Consider the function f(x)= 2x2 + 6x – 7. 1. Determine whether the graph opens upward or downward. 2. Find the axis of symmetry. 3. Find the vertex. 4. Identify the maximum or minimum value of the function. 5. Find the y-intercept. upward x = –1.5 (–1.5, –11.5) min.: –11.5 –7

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Lesson Quiz: Part II Consider the function f(x)= 2x2 + 6x – 7. 6. Graph the function. 7. Find the domain and range of the function. D: All real numbers; R {y|y ≥ –11.5}

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