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 3.1 - Page 344: 64

Answer

The two numbers are $12$ and $-12.$ Minimum product: $-144$

Work Step by Step

See p.340: Strategy for Solving Problems lnvolving Maximizing or Minimizing Quadratic Functions 1. $\quad $Read the problem carefully and decide which quantity is to be maximized or minimized. 2. $\quad $Use the conditions of the problem to express the quantity as a function in one variable. 3. $\quad $Rewrite the function in the form $f(x)=ax^{2}+bx+c$. 4. $\quad $Calculate $-\displaystyle \frac{b}{2a}$. If $a>0, f$ has a minimum of $f$($-\displaystyle \frac{b}{2a}$) at $x=-\displaystyle \frac{b}{2a}$. If $a<0, f$ has a maximum of $f$($-\displaystyle \frac{b}{2a}$) at $x==-\displaystyle \frac{b}{2a}$ 5. $\quad $Answer the question posed in the problem. ---------------------------- 1. Product is to be minimized 2. Let $x$ be the greater of the numbers. Then, the other number is $x-24$ Their product, $f(x)=x(x-24)$ is a quadratic function. 3.$\quad f(x)=x^{2}-24x$ $4.\qquad a=1, b=-24, c=0$ $-\displaystyle \frac{b}{2a}=-\frac{-24}{2(1)}=12$ 5. $a > 0,$ The product is minimum when $x=12$ The other number is $12-24=-12.$ The minimum product is $f(12)=12(-12)=-144$
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