College Algebra (10th Edition)

Published by Pearson
ISBN 10: 0321979478
ISBN 13: 978-0-32197-947-6

Chapter 4 - Section 4.3 - Quadratic Functions and Their Properties - 4.3 Assess Your Understanding - Page 301: 81

Answer

a) $x = -2$ b) $x = 3, -7$ c) $x = 0, -4$ d) see graph

Work Step by Step

$f(x) = x^2 + 4x - 21$ $a = 2$, $b = 4$ $c = -21$ a) Vertex of f(x) $x = \frac{-b}{2a} = -2$ b)x-intercepts Solution $f(x) = 0$ will give x-intercepts $\Rightarrow x^2 + 4x - 21 = 0$ $\Rightarrow (x-3)(x+7) = 0$ $\Rightarrow x = 3, -7$ c) $f(x) = -21$ $\Rightarrow x^2 + 4x - 21 = -21$ $\Rightarrow x(x+4) = 0$ $\Rightarrow x = 0, -4$
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