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: 84

Answer

Short leg: $3.1$ feet Long leg: $5.1$ feet

Work Step by Step

Let's note: $s$=the shorter leg $l$=the longer leg $h$=the hypotenuse We are given: $$\begin{align*} h&=6\\ s&=l-2\ \end{align*}$$ Use the Pythagorean theorem: $$\begin{align*} h^2&=s^2+l^2\\ 6^2&=(l-2)^2+l^2\\ 36&=l^2-4l+4+l^2\\ 0&=2l^2-4l+4-36\\ 0&=2l^2-4l-32\\ 0&=l^2-2l-16. \end{align*}$$ Solve the equation using the Quadratic Formula: $$\begin{align*} l^2-2l-16&=0\\ l&=\dfrac{-(-2)\pm\sqrt{(-2)^2-4(1)(-16)}}{2(1)}\\ &=\dfrac{2\pm 8.25}{2}\\ l_1&\approx -3.1\\ l_2&\approx 5.1. \end{align*}$$ As $l>0$, the only solution is $l=5.1$. Determine $s$: $$\begin{align*} s&=l-2=5.1-2=3.1\ \end{align*}$$
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