Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 3 - Polynomial and Rational Functions - 3.3 Zeros of Polynomial Functions - 3.3 Exercises - Page 337: 63

Answer

$$\color{blue}{ f(x)=x^5-2x^4+3x^3-2x^2+2x }$$

Work Step by Step

We are given zeros and asked to write a polynomial function. If $ 0 $ is a zero, then our factor is $\bf{(x )}$ because when $x= 0 $, $(0 )=0$ If $ i $ is a zero, then $n+ i =0$ $n = -i $ So our factor is $\bf{(x -i )}$ because when $x= i $, $(x -i )=0$ Since $ i $ is a complex number, its conjugate, $-i$, is also a zero $n -i =0$ $n= i $ So our factor is $\bf{(x+i )}$ because when $x= - i $, $(x+i )=0$ If $ 1+i $ is a zero, then $n +1+i =0$ $n +i = -1 $ $n= -1-i $ So our factor is $\bf{(x -1-i )}$ because when $x= 1+i $, $(x-1-i )=0$ Since $ 1+i $ is a complex number, its conjugate, $1-i$, is also a zero $n +1-i =0$ $n -i = -1 $ $n= -1+i $ So our factor is $\bf{(x -1+i )}$ because when $x= 1-i $, $(x-1+i )=0$ So our function is: $f(x)=(x)(x-i)(x+i)(x-1-i)(x-1+i)$ $f(x)=(x)(x-i)(x+i)(x^2-2x+1-i^2)$ Recall that $i^2=-1$ $f(x)=(x)(x-i)(x+i)(x^2-2x+1-(-1))$ $f(x)=(x)(x-i)(x+i)(x^2-2x+2)$ $f(x)=(x)(x^2+ix-ix-i^2)(x^2-2x+2)$ $f(x)=(x)(x^2-(-1))(x^2-2x+2)$ $f(x)=(x)(x^2+1)(x^2-2x+2)$ $f(x)=(x^3+x)(x^2-2x+2)$ $f(x)=x^5-2x^4+2x^3+x^3-2x^2+2x$ $$\color{blue}{ f(x)=x^5-2x^4+3x^3-2x^2+2x }$$
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