College Algebra (6th Edition)

Published by Pearson
ISBN 10: 0-32178-228-3
ISBN 13: 978-0-32178-228-1

Chapter 3 - Polynomial and Rational Functions - Exercise Set 3.4 - Page 387: 32

Answer

$f(x)=3x^{4}-x^{3}-9x^{2}+159x-52$

Work Step by Step

The Linear Factorization Theorem... in words: An nth-degree polynomial can be expressed as the product of a nonzero constant and $n$ linear factors, where each linear factor has a leading coefficient of 1. Imaginary roots, if they exist, occur in conjugate pairs. ------------------------- If $(2+3i)$ is a zero, so is $(2-3i).$ $f(x)=a_{n}(x-\displaystyle \frac{1}{3})(x+4)(x-2+3i)(x-2-3i)$ ... factor 1/3 out of the first parentheses... $f(x)=\displaystyle \frac{a_{n}}{3}(3x-1)(x+4)(x-2+3i)(x-2-3i)$ $f(x)=\displaystyle \frac{a_{n}}{3}(3x^{2}+11x-4)(x^{2}-2x-3ix-2x+4+6i+3ix-6i-9i^{2})$ $f(x)=\displaystyle \frac{a_{n}}{3}(3x^{2}+11x-4)(x^{2}-4x+13)$ Using the given $f(1),$we find $\displaystyle \frac{a_{n}}{3}:$ $f(1)=\displaystyle \frac{a_{n}}{3}(3+11-4)(1-4+13)$ $100=\displaystyle \frac{a_{n}}{3}(10)(10)$ $100=\displaystyle \frac{a_{n}}{3}(100)$ $\displaystyle \frac{a_{n}}{3}=1$ $f(x)=1\cdot(3x^{2}+11x-4)(x^{2}-4x+13)$ $f(x)=3x^{4}-12x^{3}+39x^{2}+11x^{3}-44x^{2}+143x-4x^{2}+16x-52$ $f(x)=3x^{4}-x^{3}-9x^{2}+159x-52$
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