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 8.2 - The Quadratic Formula - Exercise Set - Page 609: 82

Answer

Length $=6.2$ inches. Width $=1.6$ inches.

Work Step by Step

Let the length be $l$. and width be $w$. Area of the rectangle is $A=l\cdot w$ ... (1) From the question we have $l=2w+3$ ... (2) $A=10$ square inches. By using equation (1) and (2). $10=(2w+3)\cdot w$ Simplify. $10=2w^2+3w$ Subtract $10$ from both sides. $10-10=2w^2+3w-10$ $0=2w^2+3w-10$ The quadratic equation is $2w^2+3w-10=0$ By using quadratic equation solution. $w=\frac{-3 \pm \sqrt {3^2-4(2)(-10)}}{2(2)}$ $w=\frac{-3\pm \sqrt {9+80}}{4}$ $w=\frac{-3\pm \sqrt {89}}{4}$ Take positive value. $w=\frac{-3+ \sqrt {89}}{4}$ $w=1.60849528301$ Round to the nearest tenth of an inch. $w=1.6$ inches. Plug the value of $w$ into equation (2). $l=2(1.6)+3$ $l=3.2+3$ $l=6.2$ inches.
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