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: 22

Answer

$f(x)=x^5-5x^4+11x^3-13x^2+8x-2$

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: $1 \pm i$ and $1$ with multiplicity $3$. We write the factors of the function as $(x-zero)^{multiplicity}$ and multiply them to get the polynomial. Therefore, we can write the equation of the function as: $f(x)=[x-(1+i)][(x-(1-i)](x-1)(x-1)(x-1)\\=(x-1-i)(x-1+i)(x-1)^3\\=(x^2-2x+1+1)(x^3-3x^2+ 3x - 1)\\=(x^2-2x+2)(x^3 - 3 x^2 + 3 x - 1)\\=x^5-5x^4+11x^3-13x^2+8x-2$
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