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: 43

Answer

$P(x)=(x-2)^2(x+3)(2x-1)(x^{2}+1)..$ zeros: $\quad -3, \ 1/2,\ \ 2, $

Work Step by Step

$P(x)=2x^{6}-3x^{5}-13x^{4}+29x^{3}-27x^{2}+32x-12,$ ($5$ sign variations, we expect $5,3,$ or $1$ real zeros) $P(-x)=2x^{6}+3x^{5}-13x^{4}-29x^{3}-27x^{2}-32x-12,$ ($1$ sign variations, we expect $1$ negative real zero) $a_{0}=-12 \quad $p: $\pm 1,\pm 2,\pm 3,\pm 4,\pm 6,\pm 12$ $a_{n}=2,\qquad $q: $\pm 1,\pm 2$ Possible rational zeros $\displaystyle \frac{p}{q}:\quad$ with synthetic division, we try$ \pm$1, $\pm$2,... $\begin{array}{r|rrrrrrrrrrr}\hline 2 & 2 & -3 & -13 & 29 & -27 & 32 & -12 \\ & & 4 & 2 & -22 & 14 & -26 & 12 \\ \hline & 2 & 1 & -11 & 7 & -13 & 6 & 0 \\ & & & \swarrow & & & & \\ 2 & 2 & 1 & -11 & 7 & -13 & 6 & \\ & & 4 & 10 & -2 & 10 & -6 & \\ \hline & 2 & 5 & -1 & 5 & -3 & 0 & \\ & & & \swarrow & & & & \\ -3 & 2 & 5 & -1 & 5 & -3 & & \\ & & -6 & 3 & -6 & 3 & & \\ \hline & 2 & -1 & 2 & -1 & 0 & & \\ & & & \swarrow & & & & \\ 1/2 & 2 & -1 & 2 & -1 & & & \\ & & 1 & 0 & 1 & & & \\ \hline & 2 & 0 & 2 & 0 & & & \\ \end{array}$ $P(x)=(x-2)(x-2)(x+3)(x-\displaystyle \frac{1}{2})(2x^{2}+2).$ the last term has no real zeros. $ P(x)=(x-2)(x-2)(x+3)(x-\displaystyle \frac{1}{2})\cdot$2$(x^{2}+$1$)$ $P(x)=(x-2)(x-2)(x+3)(2x-1)(x^{2}+1)..$ zeros: $\quad -3, 1/2, 2, $
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