Functions Modeling Change: A Preparation for Calculus, 5th Edition

Published by Wiley
ISBN 10: 1118583191
ISBN 13: 978-1-11858-319-7

Chapter 3 - Quadratic Functions - Review Exercises and Problems for Chapter Three - Page 130: 26

Answer

Vertex: $(1,-4)$ Zeros: $x= \pm \sqrt{2 }+1$

Work Step by Step

We have $y=2 x^2-4 x-2=2\left(x^2-2 x-1\right)$. Completing the square, we get $$ \begin{aligned} y & =2\left(x^2-2 x+1^2-1^2-1\right) \\ & =2(x-1)^2-4 \end{aligned} $$ The vertex is at $(1,-4)$. The zeros occur when $y=0$, so $$ \begin{aligned} & 0=2(x-1)^2-4 \\ & 2=(x-1)^2 \\ & x= \pm \sqrt{2}+1 \end{aligned} $$
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