Intermediate Algebra for College Students (7th Edition)

Published by Pearson
ISBN 10: 0-13417-894-7
ISBN 13: 978-0-13417-894-3

Chapter 8 - Section 8.3 - Quadratic Functions and Their Graphs - Exercise Set - Page 627: 61

Answer

The pair is $-8$ and $8$. The minimum product is $-64$.

Work Step by Step

The given difference of the numbers in the pair is $16$. Let's note by $x$ one of the numbers of the pair whose product is minimum. The other number is $x+16$. The product is $\Rightarrow P(x)=x(x+16)$ Use the distributive property. $\Rightarrow P(x)=x^2+16x$. The standard form of a quadratic equation is $f(x)=ax^2+bx+c$. Compare both equations to identify the constants $a=1$, $b=16$, $c=0$. The value of $a$ is greater than zero, the function has the minimum value. The value of $x$ for which the minimum is reached is $-\frac{b}{2a}$. Substitute all values. $\Rightarrow x=-\frac{16}{2(1)}$. Simplify. $\Rightarrow x=-8$. The other number is $x+16=-8+16=8$. Hence, the pair is $-8$ and $8$. The minimum product is $8(-8)=-64$.
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