College Algebra 7th Edition

Published by Brooks Cole
ISBN 10: 1305115546
ISBN 13: 978-1-30511-554-5

Chapter 3, Polynomial and Rational Functions - Section 3.5 - Complex Zeros and the Fundamental Theorem of Algebra - 3.5 Exercises - Page 330: 64

Answer

$x \in \{-i, i, 2 \}$ The zeros $-i$ and $i$ have multiplicity $2$.

Work Step by Step

$P(x)=x^5-2x^4+2x^3-4x^2+x-2$ Factorize the polynomial: $x^4(x-2)+2x^2(x-2)+1(x-2)=(x-2)(x^4+2x^2+1)$, Solve for the trinomial: let's let $x^2=k$. $k^2+2k+1$ Factorize the trinomial $(k^2+2k+1)$, (find two factors of $1$ whose sum is $2$: ($1$ and $1$)) $k^2+2k+1=k^2+k+k+1=(k+1)^2$. Replace $x^2=k$: $(x^2+1)^2$ Thus, the zeros are: $(x-2)(x^2+1)^2=0$ $x \in \{-i, i, 2 \}$ The zeros $-i$ and $i$ have multiplicity $2$.
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