Intermediate Algebra (6th Edition)

Published by Pearson
ISBN 10: 0321785045
ISBN 13: 978-0-32178-504-6

Chapter 7 - Section 7.4 - Adding, Subtracting, and Multiplying Radical Expressions - Exercise Set - Page 440: 86

Answer

the perimeter is $\left( 12\sqrt{3}+13\sqrt{7} \right) \text{ meters}$; the area is $39\sqrt{21} \text{ square meters}$

Work Step by Step

Adding all the given sides of the trapezoid, then its perimeter, $P,$ is \begin{array}{l}\require{cancel} P=2\sqrt{27}+2\sqrt{63}+6\sqrt{3}+7\sqrt{7} .\end{array} Extracting the factor of the radicand that is a perfect power of the index, the equation above is equivalent to \begin{array}{l}\require{cancel} P=2\sqrt{9\cdot3}+2\sqrt{9\cdot7}+6\sqrt{3}+7\sqrt{7} \\ P=2\sqrt{(3)^2\cdot3}+2\sqrt{(3)^2\cdot7}+6\sqrt{3}+7\sqrt{7} \\ P=2(3)\sqrt{3}+2(3)\sqrt{7}+6\sqrt{3}+7\sqrt{7} \\ P=6\sqrt{3}+6\sqrt{7}+6\sqrt{3}+7\sqrt{7} \\ P=\left( 6\sqrt{3}+6\sqrt{3}\right) +\left(6\sqrt{7}+7\sqrt{7}\right) \\ P=12\sqrt{3}+13\sqrt{7} .\end{array} Hence, the perimeter, $P,$ is $ \left( 12\sqrt{3}+13\sqrt{7} \right) \text{ meters} .$ Using $A=\dfrac{h(b_1+b_2)}{2}$ or the formula for the area of a trapezoid, then \begin{array}{l}\require{cancel} A=\dfrac{6\sqrt{3}(2\sqrt{63}+7\sqrt{7})}{2} .\end{array} Extracting the factor of the radicand that is a perfect power of the index, the equation above is equivalent to \begin{array}{l}\require{cancel} A=\dfrac{6\sqrt{3}(2\sqrt{9\cdot7}+7\sqrt{7})}{2} \\ A=\dfrac{6\sqrt{3}(2\sqrt{(3)^2\cdot7}+7\sqrt{7})}{2} \\ A=\dfrac{6\sqrt{3}(2(3)\sqrt{7}+7\sqrt{7})}{2} \\ A=\dfrac{6\sqrt{3}(6\sqrt{7}+7\sqrt{7})}{2} \\ A=\dfrac{6\sqrt{3}(13\sqrt{7})}{2} \\ A=\dfrac{\cancel2\cdot3\sqrt{3}(13\sqrt{7})}{\cancel2} \\ A=3\sqrt{3}(13\sqrt{7}) \\ A=39\sqrt{21} .\end{array} Hence, the area, $A,$ is $ 39\sqrt{21} \text{ square meters} .$
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