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: 83

Answer

Short leg: $17.6$ inches Long leg: $18.6$ inches Hypotenuse: $25.6$ inches

Work Step by Step

Let's note: $s$=the shorter leg $l$=the longer leg $h$=the hypotenuse We are given: $$\begin{align*} l&=s+1\\ h&=l+7\ \end{align*}$$ Rewrite $h$ in terms of $s$: $$h=l+7=s+1+7=s+8.$$ Use the Pythagorean theorem: $$\begin{align*} h^2&=s^2+l^2\\ (s+8)^2&=s^2+(s+1)^2\\ s^2+16s+64&=s^2+s^2+2s+1\\ 0&=2s^2+2s+1-s^2-16s-64\\ 0&=s^2-14s-63. \end{align*}$$ Solve the equation using the Quadratic Formula: $$\begin{align*} s^2-14s-63&=0\\ s&=\dfrac{-(-14)\pm\sqrt{(-14)^2-4(1)(-63)}}{2(1)}\\ &=\dfrac{14\pm 21.17}{2}\\ s_1&\approx -3.6\\ s_2&\approx 17.6. \end{align*}$$ As $s>0$, the only solution is $s=17.6$. Determine $l$ and $h$: $$\begin{align*} l&=s+1=17.6+1=18.6\\ h&=s+8=17.6+8=25.6\ \end{align*}$$
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