College Algebra 7th Edition

Published by Brooks Cole
ISBN 10: 1305115546
ISBN 13: 978-1-30511-554-5

Chapter 1, Equations and Graphs - Section 1.4 - Solving Quadratic Equations - 1.4 Exercises - Page 125: 88

Answer

Circle: $190.8$ inches Square: $169.2$ inches

Work Step by Step

Let's note: $r$ = the radius of the circle $x$ = the length of the square's side. We are given: $$\begin{cases} 2\pi r+4x&=360\\ \pi r^2&=x^2. \end{cases}$$ Use the substitution method to solve the system: $$\begin{align*} r&=\dfrac{360-4x}{2\pi}=\dfrac{180-2x}{\pi}\\ \pi \left(\dfrac{180-2x}{\pi}\right)^2&=x^2\\ (180-2x)^2&=\pi x^2\\ 180-2x&=\pm\sqrt{\pi}x\\ 180&=2x\pm\sqrt{\pi}x\\ 180&=x(2\pm\sqrt{\pi})\\ x&=\dfrac{180}{2\pm\sqrt{\pi}}\\ x_1&=\dfrac{180}{2-\sqrt{\pi}}\approx 791\\ x_2&=\dfrac{180}{2+\sqrt{\pi}}\approx 47.7. \end{align*}$$ Because $x<360$, only the solution $x=47.7$ fits. Determine the length of the square piece: $$4x=4(47.7)=190.8.$$ Determine the length of the circle piece: $$2\pi r=360-190.8.=169.2$$
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