Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 1 - Equations and Inequalities - 1.5 Applications and Modeling with Quadratic Equations - 1.5 Exercises - Page 130: 19

Answer

$$6,8,10$$

Work Step by Step

Recall the Pythagorean Theorem, $a^2+b^2=c^2$ where $a$ and $b$ are the legs of the right triangle and $c$ is the hypotenuse. If the sides of the triangle are three consecutive even integers, the triangle can be represented by: $a=x$, $b=(x+2)$, and $c=(x+4)$ $x^2 + (x+2)^2 = (x+4)^2$ $x^2 + x^2 +4x+4 = x^2+8x+16$ Combine like terms all on one side in standard quadratic equation form: $ax^2 + bx +c=0$ $x^2-4x-12=0$ now, apply the quadratic formula: $x=\dfrac{-b\pm\sqrt{b^2-4ac}}{2a}$ where $a=1$, $b=-4$, and $c=-12$ $x=\dfrac{4\pm\sqrt{(-4)^2-4(1)(-12)}}{2(1)}$ $x=\dfrac{4\pm\sqrt{16+48}}{2}$ $x=\dfrac{4\pm\sqrt{64}}{2}$ $x=\dfrac{4\pm8}{2}$ $x=\dfrac{4+8}{2}$ or $x=\dfrac{4-8}{2}$ $x=\dfrac{12}{2}$ or $x=\dfrac{-4}{2}$ $x=6$ or $x=-2$ Since the length of a side can not be negative, we know that $x=6$ Therefore the sides of the triangle are: $6, (6+2), (6+4)$ $$6,8,10$$
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