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: 24

Answer

$P(x)=x(x-\displaystyle \frac{1}{2}-\frac{\sqrt{3}}{2}i)(x-\frac{1}{2}+\frac{\sqrt{3}}{2}i)$ Zeros: 0, $\displaystyle \frac{1}{2}-\frac{\sqrt{3}}{2}i,\ \displaystyle \frac{1}{2}+\frac{\sqrt{3}}{2}i$ (all with multiplicity 1)

Work Step by Step

Factoring x out of all three terms, $P(x)=x(x^{2}-x+1)$ Zeros of $x^{2}-x+1$ , (quadratic formula) $x=\displaystyle \frac{-b\pm\sqrt{b^{2}-4ac}}{2a},\quad a=1, b=-1, c=1$ $x=\displaystyle \frac{1\pm\sqrt{1-4(1)(1)}}{2(1)}=\frac{1\pm\sqrt{-3}}{2}$ $x=\displaystyle \frac{1}{2}\pm\frac{\sqrt{3}}{2}i$ $P(x)=x[x-(\displaystyle \frac{1}{2}+\frac{\sqrt{3}}{2}i)][x-(\frac{1}{2}-\frac{\sqrt{3}}{2}i)]$ $P(x)=x(x-\displaystyle \frac{1}{2}-\frac{\sqrt{3}}{2}i)(x-\frac{1}{2}+\frac{\sqrt{3}}{2}i)$ Zeros: 0, $\displaystyle \frac{1}{2}-\frac{\sqrt{3}}{2}i,\ \displaystyle \frac{1}{2}+\frac{\sqrt{3}}{2}i$ (all with multiplicity 1)
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