Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 3 - Section 3.4 - Real Zeros of Polynomials - 3.4 Exercises - Page 284: 31

Answer

Zeros:$\displaystyle \quad\pm 2,3,\frac{1}{3}$ $P(x)= (3x-1)(x-2)(x+2)(x-3)$

Work Step by Step

Possible rational zeros: $\displaystyle \quad \frac{p}{q}$ where$\left\{\begin{array}{llllll} p: & \pm 1 & \pm 2, & \pm 3, & \pm 6, & \pm 12\\ q: & \pm 1 & \pm 3 & & & \end{array}\right.$ $P(x)$ has 3 sign changes, we expect 3 or 1 positive real zeros. With synthetic division, we try the integers first. 1 is not a zero ... try 2: \begin{array}{rrrrrrr} 2 \ \rceil & 3 & -10 & -9 & 40 & -12 & \\ & & 6 & -8 & -34 & 12 & \\ \hline & 3 & -4 & -17 & 6 & 0 & \\ & & & & & & \\ 3 \ \rceil & 3 & -4 & -17 & 6 & & \\ & & 9 & 15 & -6 & & \\ \hline & 3 & 5 & -2 & 0 & & \\ & & & & & & \\ -2 \ \rceil & 3 & 5 & -2 & & & \\ & & -6 & 2 & & & \\ \hline & 3 & -1 & 0 & & &P(x)= (3x-1)(x-2)(x+2)(x-3) \\ & & & & & & \\ 1/3 \ \rceil & 3 & -1 & & & & \\ & & 1 & & & & \\ \hline & 3 & 0 & & & & \\ \end{array} Zeros:$\displaystyle \quad\pm 2,3,\frac{1}{3}$ P(x)= (3x-1)(x-2)(x+2)(x-3)
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