Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 2 - Test - Page 434: 14

Answer

There are three positive roots and no negative roots of the polynomial among which two can be real in nature.

Work Step by Step

It can be observed from the given polynomial that it changes signs three times. Then, according to Descartes' Rule of Signs, the polynomial can have a maximum of 3 positive roots. Now, substituting x with $-x$, we obtain: $\begin{align} & f\left( -x \right)=3{{\left( -x \right)}^{5}}-2{{\left( -x \right)}^{4}}-2{{\left( -x \right)}^{2}}+\left( -x \right)-1 \\ & f\left( -x \right)=-3{{\left( x \right)}^{5}}-2{{\left( x \right)}^{4}}-2{{\left( x \right)}^{2}}-\left( x \right)-1 \\ \end{align}$ Then, it can be seen that the polynomial remains negative throughout; hence, it has no negative roots. Thus, the polynomial has three positive roots and no negative roots.
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.