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Completing the Square to Solve a Quadratic
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Completing the Square: A new Way to Solve Quadratics We have seen how to solve the equation below by taking the square root: But, this method only works if the equation is identical to the one above (a perfect square trinomial equals a number). It would be useful to learn how to rewrite an equation (like the one below) so it is identical to the one above. Then, you can apply the square root technique.
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+ – Completing the Square to Solve a Quadratic + – Solve: = Try to make a Square with the tiles Complete the square by adding the unit tiles needed to make a perfect square to both sides. Factor the perfect square trinomial Since there is one x, you can square root to solve Never complete the square by adding additional variables
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Perfect Square A polynomial that can be factored into the following form: (x + a) 2 Examples:
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Completing the Square x 2 + bx + c is a perfect square if: (The value of c will always be positive.) Ex: Prove the following is a perfect square Half of b=-16 squared is 64=c
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Completing the Square Find the c that completes the square: 1.x 2 + 50x + c 2.x 2 – 22x + c 3.x 2 + 15x + c
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Factoring a Completed Square If x 2 + bx + c is a perfect square, then it will easily factor to: Ex: Prove the following is a perfect square. Half of b=+8 is +4
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Completing the Square to Solve a Quadratic Solve the following equation by completing the square: ( x – # ) 2 = # GOAL Isolate the x terms Find the “c” that completes the square Add the “c” to both sides Factor and Simplify Solve
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Completing the Square to Solve a Quadratic Solve the following equation by completing the square: ( x – # ) 2 = # GOAL Isolate the x terms Find the “c” that completes the square Add the “c” to both sides Factor and Simplify Solve
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