College Algebra (10th Edition)

Published by Pearson
ISBN 10: 0321979478
ISBN 13: 978-0-32197-947-6

Chapter 1 - Section 1.2 - Quadratic Equations - 1.2 Assess Your Understanding - Page 104: 121

Answer

Both equations have two distinct real solutions. The solutions of one equation are the negatives of the solutions of the other.

Work Step by Step

With the assumption made by the problem text, $ax^{2}+bx+c=0$ has two real solutions , $x=\displaystyle \frac{-b\pm\sqrt{b^{2}-4ac}}{2a}$ . Name them $x_{1}=\displaystyle \frac{-b-\sqrt{b^{2}-4ac}}{2a}$ and $x_{2}=\displaystyle \frac{-b+\sqrt{b^{2}-4ac}}{2a}$ Also, by the assumption, and because $(-b)^{2}=b^{2}$, the equation $ax^{2}-bx+c=0$ has two solutions. $x=\displaystyle \frac{-(-b)\pm\sqrt{(-b)^{2}-4ac}}{2a}=\frac{b\pm\sqrt{b^{2}-4ac}}{2a}$ Let $x_{3}=\displaystyle \frac{b-\sqrt{b^{2}-4ac}}{2a}$ Then , $x_{3}=-\displaystyle \frac{-b+\sqrt{b^{2}-4ac}}{2a}=-x_{2}$ And let $x_{4} =\displaystyle \frac{b+\sqrt{b^{2}-4ac}}{2a}$. Then, $x_{4}=-\displaystyle \frac{-b-\sqrt{b^{2}-4ac}}{2a}=-x_{1}$ Both equations have two distinct real solutions. The solutions of one equation are the negatives of the solutions of the other.
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