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: 59

Answer

$$\color{blue}{\bf{f(x)= 5 x^3 -10x^2+5x }}$$

Work Step by Step

We are given three zeros of a polynomial and the value of the function for a given ${x}$: Our zeros are $\bf{ 0 }$ and $\bf{ 1 }$ of multiplicity 2 so let's make them into factors of our polynomial. If $\bf{ 0 }$ is a zero then: $( 0 +n)=0$ $n= 0 $ so our factor is $\bf{(x )}$ because when $x=\bf{ 0 }$, $(x +0 )=0$ If $\bf{ 1 }$ is a zero then: $( 1 +n)=0$ $n= -1 $ so our factor is ${(x -1 )}$ because when $x=\bf{ 1 }$, $(x -1 )=0$ Since $\bf{ 1 }$ is a zero of multiplicity 2, $(x -1 )$ is a factor twice: $\bf{(x -1 )^2}$ or $\bf{(x -1 )(x -1 )}$ Now we have three factors of our 3rd degree polynomial: $\bf{(x )(x -1 )(x -1 )}$, which, multiplied by some unknown factor $a$, make up our function: $f(x)=a(x )(x -1 )(x -1 )$ If $f( 2 )= 10 $ then ${(2 )(2 -1 )( 2 -1 )}$ times some number $a$, equals $ 10 $ or: $f( 2 )= 10 =a (2 )(2 -1 )( 2 -1 ) $ $10 =a (2 )(1 )( 1 ) $ $10 =a (2 ) $ $\bf{a= 5 }$ Now that we have the value of $a$, we can find $f(x)$ $f(x)=5 (x )(x -1 )(x -1 ) $ $f(x)=5 (x^2 -x )(x -1 ) $ $f(x)=5 (x^3 -2x^2+x ) $ $$\color{blue}{\bf{f(x)= 5 x^3 -10x^2+5x }}$$
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