Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

Published by Pearson
ISBN 10: 0-32184-874-8
ISBN 13: 978-0-32184-874-1

Chapter 11 - Quadratic Functions and Equations - 11.3 Studying Solutions of Quadratic Equations - 11.3 Exercise Set - Page 719: 68

Answer

Hence, prooved

Work Step by Step

For the equation $a{{x}^{2}}+bx+c=0$, use the quadratic formula to solve for the value of x. Hence the two solutions are, $x=\frac{-b+\sqrt{{{b}^{2}}-4ac}}{2a}$ Or, $x=\frac{-b-\sqrt{{{b}^{2}}-4ac}}{2a}$ The product of the solutions is $\left( \frac{-b+\sqrt{{{b}^{2}}-4ac}}{2a} \right)\left( \frac{-b-\sqrt{{{b}^{2}}-4ac}}{2a} \right)$. By the formula ${{a}^{2}}-{{b}^{2}}=\left( a-b \right)\left( a+b \right)$ the product is: $\begin{align} & \frac{{{\left( -b \right)}^{2}}-{{\left( \sqrt{{{b}^{2}}-4ac} \right)}^{2}}}{{{\left( 2a \right)}^{2}}}=\frac{{{b}^{2}}-\left( {{b}^{2}}-4ac \right)}{4{{a}^{2}}} \\ & =\frac{{{b}^{2}}-{{b}^{2}}+4ac}{4{{a}^{2}}} \\ & =\frac{4ac}{4{{a}^{2}}} \\ & =\frac{c}{a} \end{align}$ Thus, the product of the solutions is $\frac{c}{a}$.
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