Big Ideas Math - Algebra 1, A Common Core Curriculum

Published by Big Ideas Learning LLC
ISBN 10: 978-1-60840-838-2
ISBN 13: 978-1-60840-838-2

Chapter 9 - Solving Quadratic Equations - 9.5 - Solving Quadratic Equations Using the Quadratic Formula - Exercises - Page 521: 39

Answer

The solutions are $x\approx 0.74$ and $x\approx -6.74$.

Work Step by Step

The given equation is $\Rightarrow x^2+6x=5$ The coefficient of the $x^2-$term is $1$, and the coefficient of the $x-$term is an even number. So, solve by completing the square. $\Rightarrow x^2+6x=5$ Add $(\frac{b}{2})^2=(\frac{6}{2})^2=9$ to each side. $\Rightarrow x^2+6x+9=5+9$ Write the left side as the square of a binomial. $\Rightarrow (x+3)^2=14$ Take the square root of each side. $\Rightarrow x+3=\pm\sqrt{14}$ Subtract $3$ from each side. $\Rightarrow x+3-3=-3\pm\sqrt{14}$ Simplify. $\Rightarrow x=-3\pm\sqrt{14}$ The solutions are $x=-3+\sqrt{14}\approx 0.74$ and $x=-3-\sqrt{14}\approx -6.74$.
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