Precalculus (6th Edition) Blitzer

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

Chapter 2 - Section 2.5 - Zeros of Polynomial Functions - Exercise Set - Page 377: 11

Answer

a. $\frac{p}{q}=\pm1,\pm2,\pm3,\pm6,\pm\frac{1}{2},\pm\frac{3}{2}$ b. $x=\frac{1}{2}$ see figure. c. $x=-2,\frac{1}{2},3$

Work Step by Step

a. Given the function $f(x)=2x^3-3x^2-11x+6$ we have $p=\pm1,\pm2,\pm3,\pm6$ and $q=\pm1,\pm2$ and the possible rational zeros are $\frac{p}{q}=\pm1,\pm2,\pm3,\pm6,\pm\frac{1}{2},\pm\frac{3}{2}$ b. Starting from the lowest, test the possible rational zeros using synthetic division. We can find $x=\frac{1}{2}$ as a zero as shown in the figure. c. Based on the results from part-b, we have $f(x)=2x^3-3x^2-11x+6=(x-\frac{1}{2})(2x^2-2x-12)=(2x-1)(x^2-x-6)=(2x-1)(x-3)(x+2)$ Thus the zeros are $x=-2,\frac{1}{2},3$
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