Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Published by Pearson
ISBN 10: 0-32193-104-1
ISBN 13: 978-0-32193-104-7

Chapter 3 - Polynomial and Rational Functions - Section 3.3 Complex Zeros; Fundamental Theorem of Algebra - 3.3 Assess Your Understanding - Page 231: 20

Answer

$x^6-12x^5+55x^4-120x^3+139x^2-108x+85$

Work Step by Step

The Conjugate Pairs Theorem states that when a polynomial has real coefficients, then any complex zeros occur in conjugate pairs. This means that, when $(p +i \ q)$ is a zero of a polynomial function with a real number of the coefficients, then its conjugate $(p –i q)$, is also a zero of the function. We are given that the zeros of the function are: $2 \pm i, 4 \pm i, \pm i$. We write the factors of the function as $(x-zero)$ and multiply them to get the polynomial. Therefore, we can write the equation of the function as: $f(x)=[x-(2+i)][x-(2-i)](x-i)(x-i)(x-(-i))[(x-(4-i)][x-(4+i)] \\=(x-2-i)(x-2+i)(x-i)(x+i)(x-4+i)(x-4-i) \\=x^6-12x^5+55x^4-120x^3+139x^2-108x+85$
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