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 - 11.2 The Quadratic Formula - 11.2 Exercise Set - Page 714: 65


$$z=.339, -1.179$$

Work Step by Step

There are many ways to solve these problems. However, it is beneficial to use the quadratic formula, for this will work for almost any expression. Hence, we find: $$ 100z^2+84z-40=0\\ z_{1,\:2}=\frac{-84\pm \sqrt{84^2-4\cdot \:100\left(-40\right)}}{2\cdot \:100}\\ z=\frac{-21+\sqrt{1441}}{50},\:z=-\frac{21+\sqrt{1441}}{50} \\ z=.339, -1.179$$
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