Intermediate Algebra: Connecting Concepts through Application

Published by Brooks Cole
ISBN 10: 0-53449-636-9
ISBN 13: 978-0-53449-636-4

Chapter 8 - Radical Functions - 8.5 Complex Numbers - 8.5 Exercises - Page 663: 82

Answer

$2 - \frac{1}{3}\sqrt{42}\ i$; $2 + \frac{1}{3}\sqrt{42}\ i$

Work Step by Step

Given the quadratic equation \begin{equation} -3 w^2+12 w-26=0. \end{equation} Factor out $-1$: $$3 w^2-12 w+26=0.$$ The quadratic equation can be best solved by the quadratic formula. We identify the constants $a$, $b$, $c$ from the general form of the equation and solve it using the quadratic formula: \begin{equation} \begin{aligned} a&x^2+bx+c=0\\ a & =3, b=-12, c=26 \\ x & =\frac{-b \pm \sqrt{b^2-4 a c}}{2 a} \\ x & =\frac{12 \pm \sqrt{(-12)^2-4 \cdot 3\cdot(26)}}{2 \cdot 3}\\ & =\frac{12\pm \sqrt{-168}}{6} \\ & =\frac{12\pm 2\sqrt{42} i}{6} \\ & =\frac{6\pm \sqrt{42} i}{3}. \end{aligned} \end{equation} The solution is \begin{equation} \begin{aligned} x&= 2 - \frac{1}{3}\sqrt{42}\ i\\ x& = 2 + \frac{1}{3}\sqrt{42}\ i. \end{aligned} \end{equation}
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