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Do Now 4/15/10 Take out HW from yesterday. Practice worksheet 10.2 form B odds Practice worksheet 10.2 form B odds Copy HW in your planner. Text p. 647, #8, 14, 17, 24, 30 Text p. 647, #8, 14, 17, 24, 30 Quiz sections Monday. Quiz sections Monday.

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Homework Practice 10.2 Form B odds 1) a = 6, b = 3, c = 5 3) a = 7, b = -3, c = -1 5) a = 3/4, b = 0, c = -10 7) up; x = 0; (0,-5) 9) down; x = 3/2; (3/2, 23/2) 11) up; x = -1; (-1, -5) 13) up; x = -5; (-5, -33/2) 15) down; x = 3/2; (3/2, -5/4) 17) down; x = 7/4; (7/4, 57/8) 19) 21) 23-31) on overhead 33) maximum; (1,3) 35) 12 ft x34567 y x0123y17/2713/2717/2

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Objective SWBAT solve quadratic equations by graphing

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Section 10.3 “Solve Quadratic Equations by Graphing” QUADRATIC EQUATION- an equation that is in the standard form ax² + bx + c = 0, where a = 0. Solve by Factoring (Chapter 9) x² - 6x + 5 = 0 (x – 1)(x – 5) = 0 x = 1 or x = 5 (Remember This???) Solve by Graphing x² - 6x + 5 = 0 To solve this equation graph y = x² - 6x + 5. From the graph you can see that the intercepts are 1 and 5. x y

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Solving Quadratic Equations by Graphing To solve a quadratic equation by graphing, first write the equation in standard form, ax² + bx + c = 0. Then graph the equation. The x-intercepts of the graph are the solutions, or roots, of the equation. Quadratic equations can have one of three types of solutions: x y (1)Two solutions x y x y (2) One solution (3) No solution Two x-intercepts One x-intercept No x-intercepts

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EXAMPLE 1 Solve a quadratic equation having two solutions Solve x 2 – 2x = 3 by graphing. STEP 1 Write the equation in standard form. Write original equation. x 2 – 2x = 3 Subtract 3 from each side. x 2 – 2x – 3 = 0 STEP 2 Graph the function y = x 2 – 2x – 3. SOLUTION The x-intercepts are – 1 and 3

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EXAMPLE 1 ANSWER The solutions of the equation x 2 – 2x = 3 are – 1 and 3. Solve a quadratic equation having two solutions You can check – 1 and 3 in the original equation. x 2 – 2x = 3 (–1) 2 –2(–1) 3 = ? (3) 2 –2(3) 3 = ? 3 = 3 Write original equation. Substitute for x. Simplify. Each solution checks. CHECK:

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EXAMPLE 2 Solve a quadratic equation having one solution Solve – x 2 + 2x = 1 by graphing. SOLUTION STEP 1 Write the equation in standard form. Write original equation. – x 2 + 2x = 1 Subtract 1 from each side. – x 2 + 2x – 1 = 0 STEP 2 Graph the function y = – x 2 + 2x – 1. The x- intercept is 1.

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EXAMPLE 3 Solve a quadratic equation having no solution Solve x = 4x by graphing. SOLUTION STEP 1 Write the equation in standard form. Write original equation. x = 4x Subtract 4x from each side. x 2 – 4x + 7 = 0 STEP 2 Graph the function y = x 2 – 4x + 7. The equation x² + 7 = 4x has no solution because there is no x- intercept.

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EXAMPLE 4 Find the zeros of a quadratic function Find the zeros of f(x) = x 2 + 6x – 7. SOLUTION Graph the function f(x) = x 2 + 6x –7. The x- intercepts are – 7 and 1. ANSWER The zeros of the function are – 7 and 1. CHECK Substitute – 7 and 1 in the original function. f(– 7) = (– 7) 2 + 6(– 7) – 7 = 0 f(1) = (1) 2 + 6(1) – 7 = 0

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Homework Text p. 647, #8, 14, 17, 24, 30 Text p. 647, #8, 14, 17, 24, 30

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