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 3.6 - Page 421: 79

Answer

Possible sides (in feet) are in $(0, 6]$ or $[19, 25)$

Work Step by Step

Let $P$ be the perimeter of a rectangle. As we are given $P = 50$ feet. The perimeter $P$ of a rectangle is given as follows: $P = 2L + 2W$ This implies $50 = 2L + 2W$ $25 = L + W$ $L = 25 – W$ … (i) Let $A$ be the area of a rectangle. As we are given $A ≤ 114$ square feet The area $A$ of a rectangle is given as follows: $A = L × W$ As per the question, the area, $A = L × W$ must not be exceeded by $114$ ft. Then $L × W ≤ 114$ Substitute $L = 25 – W$ from equation (i). $(25-W) × W ≤ 114$ $25W - W^{2} ≤ 114$ $W^{2} – 25W + 114 ≤ 0$ $W^{2} – 19W - 6W + 114 ≤ 0$ $W (W – 19) -6(W – 19) ≤ 0$ $(W- 6) (W – 19) ≤ 0$ $W = 6$ ft or $19$ ft Now, calculate $L$. $L = 25 – W$ This implies $L = 25 – 6 = 19$ ft or $L = 25 – 19 = 6$ ft Hence, $L = 19$ ft or $6$ ft and $W = 6$ ft or $19$ ft. Since $A ≤ 114$ sq ft, any length $L ≤ 19$ ft will be the possible length of a side. However, the inequality involves (less than or equal to), we must also include the solution of $W^{2} – 25W + 114 ≤ 0$, namely $6$, $19$, in the solution set. Therefore, we conclude that the possible sides (in feet) are in $(0, 6]$ or $[19, 25)$.
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