Precalculus: Mathematics for Calculus, 7th Edition

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

Chapter 3 - Section 3.5 - Complex Zeros and the Fundamental Theorem of Algebra - 3.5 Exercises - Page 293: 27

Answer

Zeros: $\displaystyle \frac{3}{2}$ , $-\displaystyle \frac{3}{2}$ , $\displaystyle \frac{3}{2}i$ , $-\displaystyle \frac{3}{2}i$, each with multiplicity 1. $P(x)=(2x-3)(2x+3)(2x-3i)(2x+3i)$

Work Step by Step

$P(x)=(4x^{2})^{2}-9^{2}= \qquad $...difference of squares... $=(4x^{2}-9)(4x^{2}+9)$ $4x^{2}-9= (2x)^{2}-3^{2}\quad $...difference of squares...$=(2x-3)(2x+3)$ $4x^{2}+9= (2x)^{2}-(-1)\cdot 3^{2}=(2x)^{2}-(3i)^{2} \qquad $...difference of squares...$=(2x-3i)(2x+3i)$ $P(x)=(2x-3)(2x+3)(2x-3i)(2x+3i)$ $\left[\begin{array}{llll} 2x-3=0 & 2x+3=0 & 2x-3i=0 & 2x+3i=0\\ 2x=3 & 2x=-3 & 3x=3i & 2x=-3i\\ x=\frac{3}{2} & x=-\frac{3}{2} & x=\frac{3}{2}i & x=-\frac{3}{2}i \end{array}\right]$ Zeros: $\displaystyle \frac{3}{2}$ , $-\displaystyle \frac{3}{2}$ , $\displaystyle \frac{3}{2}i$ , $-\displaystyle \frac{3}{2}i$, each with multiplicity 1. $P(x)=(2x-3)(2x+3)(2x-3i)(2x+3i)$
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