Algebra 2 (1st Edition)

Published by McDougal Littell
ISBN 10: 0618595414
ISBN 13: 978-0-61859-541-9

Chapter 4 Quadratic Functions and Factoring - 4.7 Complete the Square - 4.7 Exercises - Skill Practice - Page 288: 13


The trinomial $x^{2}+6x+c$ is a perfect square when $c=9.$ Then $x^{2}+6x+9=(x+3)(x+3)=(x+3)^{2}$

Work Step by Step

$ x^{2}+6x+c\qquad$ ... find half the coefficient of $x$, which is $\displaystyle \frac{6}{2}=3$. $\qquad$ ...square the result. $ 3^{2}=9\qquad$ ...substitute $c$ with $9$ in the original expression $x^{2}+6x+9=(x+3)^{2}$
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