Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 3 - Polynomial and Rational Functions - 3.3 Zeros of Polynomial Functions - 3.3 Exercises - Page 337: 43

Answer

(a) $\pm1,\pm2,\pm3,\pm4,\pm6,\pm12, \pm\frac{1}{2},\pm\frac{3}{2},\pm\frac{1}{3},\pm\frac{2}{3},\pm\frac{4}{3},\pm\frac{1}{6}$ (b) $\{-4,-\frac{1}{3},\frac{3}{2}\}$ (c) $ƒ(x)=(x+4)(3x+1)(2x-3)$

Work Step by Step

(a) Based on the given polynomial, we have factors $p=\pm1,\pm2,\pm3,\pm4,\pm6,\pm12, q=\pm1,\pm2,\pm3,\pm6$. We can list all possible rational zeros as: $\frac{p}{q}=\pm1,\pm2,\pm3,\pm4,\pm6,\pm12, \pm\frac{1}{2},\pm\frac{3}{2},\pm\frac{1}{3},\pm\frac{2}{3},\pm\frac{4}{3},\pm\frac{1}{6}$ (b) Use synthetic division and the above possible values, find one zero $x=-4$ as shown in the figure. With quotient $6x^2-7x-3=0$, we have $(3x+1)(2x-3)=0$ which gives $x=-\frac{1}{3},\frac{3}{2}$. Thus the zeros are $\{-4,-\frac{1}{3},\frac{3}{2}\}$ (c) Based on the know zeros and the factor theorem, we can factor $ƒ(x)$ into linear factors as $ƒ(x)=(x+4)(3x+1)(2x-3)$
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