Intermediate Algebra for College Students (7th Edition)

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

Chapter 7 - Section 7.4 - Adding, Subtracting, and Dividing Radical Expressions - Exercise Set - Page 539: 82

Answer

Perimeter $=24\sqrt {5}$ feet. Area $=160$ square feet.

Work Step by Step

Length of the rectangle $l=4\sqrt {20}$ feet. Width of the rectangle $w=\sqrt {80}$ feet. Perimeter: $\Rightarrow P=2l+2w$ Substitute values. $\Rightarrow P=2(4\sqrt {20})+2(\sqrt {80})$. Clear the parentheses. $\Rightarrow P=8\sqrt {5\cdot2^2}+2\sqrt {5\cdot 2^4}$. Take the square root. $\Rightarrow P=8\cdot 2\sqrt {5}+2\cdot 4\sqrt {5}$. Simplify. $\Rightarrow P=16\sqrt {5}+8\sqrt {5}$. Use the distributive property. $\Rightarrow P=(16+8)\sqrt {5}$. Simplify. $\Rightarrow P=24\sqrt {5}$. Hence, the perimeter is $24\sqrt {5}$ feet. Area : $\Rightarrow A=lw$ Substitute values. $\Rightarrow A=(4\sqrt {20})(\sqrt {80})$ Clear the parentheses. $\Rightarrow A=4\sqrt {5\cdot2^2}\cdot\sqrt {5\cdot2^4}$ Multiply the radicands and retain the common index. $\Rightarrow A=4\sqrt {5\cdot2^2\cdot5\cdot2^4}$ Simplify. $\Rightarrow A=4\sqrt {5^2\cdot2^6}$ $\Rightarrow A=4\cdot 5\cdot2^3$ Simplify. $\Rightarrow A=160$ Hence, the area is $160$ square feet.
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