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Published byDorothy Jacobs Modified over 9 years ago
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4.6 Completing the Square Completing a perfect square trinomial allows you to factor the completed trinomial as the square of a binomial. You can solve an equation that contains a perfect square by finding square roots. The simplest of this type of equation has the form ax 2 = c.
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Solving by Finding Square Roots What is the solution of each equation? A. 4x 2 + 10 = 46 4x 2 + 10 = 46 4x 2 = 36 x 2 = 9 x = ± 3
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Solving by Finding Square Roots
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Solving a Perfect Square Trinomial Equation What is the solution of x 2 + 4x + 4 = 25? Factor the perfect square trinomial. x 2 + 4x + 4 = 25 (x + 2) 2 = 25 x + 2 = ± 5 x + 2 = 5orx + 2 = -5 x = 3or x = -7 The solutions are x = 3 or x = -7.
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Completing the Square If x 2 + bx is not part of a perfect square trinomial, you can use the coefficient b to find a constant c so that x 2 + bx + c is a perfect square. When you do this, you are completing the square.
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Solving by Completing the Square What is the solution of 3x 2 – 12x + 6 = 0?
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Writing in Vertex Form What is y = x 2 + 4x – 6 in vertex form? Name the vertex and y-intercept. y = x 2 + 4x – 6 y = x 2 + 4x + 4 – 6 – 4 y = (x + 2) 2 – 6 – 4 y = (x + 2) 2 – 10 The vertex is (-2, -10). The y-intercept is (0, -6). Check with a graphing calculator.
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Writing in Vertex Form y = (x + 2) 2 – 10 The vertex is (-2, -10). The y-intercept is (0, -6). Check with a graphing calculator.
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More Practice!!!!! Homework – Textbook p. 237 – 238 #12 – 50 even.
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