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: 35

Answer

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

Work Step by Step

Possible rational zeros: $\displaystyle \quad \frac{p}{q}$ where$\left\{\begin{array}{lll} p: & \pm 1 & \pm 3\\ q: & \pm 1 & \pm 2 \end{array}\right.$ $P(x)$ has 2 sign change2, we expect 2 or 0 positive real zero. $P(-x)=-4x^{3}+7x+3$ has 1 sign change, so we expect 1 negative zero. With synthetic division, we try the integers first. try 1: \begin{array}{rrrrr} 1 \ \rceil & 4 & 0 & -7 & 3 \\ & & 4 & 4 & -3 \\ \hline & 4 & 4 & -3 & 0 \\ & & & & \\ 1/2\ \rceil & 4 & 4 & -3 & \\ & & 2 & 3 & \\ \hline & 4 & 6 & 0 & \\ & & & & \\ -3/2 \ \rceil & 4 & 6 & & \\ & & -6 & & \\ \hline & 4 & 0 & & \\ \end{array} Zeros:$\displaystyle \quad 1,\quad \frac{1}{2},\quad- \frac{3}{2}$ $P(x)=4(x-\displaystyle \frac{1}{2})(x+\frac{3}{2})(x-1)$ $=2(x-\displaystyle \frac{1}{2})\cdot 2(x+\frac{3}{2})(x-1)$ $=(2x-1)(1x+3)(x-1)$
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