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 294: 54

Answer

$3, \dfrac{1-i\sqrt 5}{2}, \dfrac{1+i\sqrt 5}{2}$

Work Step by Step

Consider $P(x)=2x^3-8x^2+9x-9=0$ In order to get the zeroes of the polynomial $P(x)$ we will have to solve as follows: $2x^3-8x^2+9x-9=(x-3)(2x^2-2x+3)=0$ This gives: $(x-3)(\dfrac{1\pm\sqrt{1-4}}{2})=0$ This can be re-written as: $(x-3)(\dfrac{2\pm\sqrt{4-24}}{4})=0$ $(x-3)(\dfrac{2\pm 2\sqrt 5 i}{2})=0 $ Thus the zeroes of $P(x)$ are: $3, \dfrac{1-i\sqrt 5}{2}, \dfrac{1+i\sqrt 5}{2}$
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