Algebra and Trigonometry 10th Edition

Published by Cengage Learning
ISBN 10: 9781337271172
ISBN 13: 978-1-33727-117-2

Chapter 3 - 3.1 - Quadratic Functions and Models - 3.1 Exercises - Page 248: 31

Answer

See explanation

Work Step by Step

Using a graphing utility, the graph is as shown. The vertex is $(3,0)$. The axis of symmetry is $x=3$. The $x$-intercept is $(3,0)$. Finding the standard form of the quadratic function: $$f(x)=-2x^2+12x-18$$ $$f(x)=-2(x^2-6x)-18$$ $$f(x)=-2\left(x^2-6x+\left(\frac{-6}{2}\right)^2\right)-18+2\left(\frac{-6}{2}\right)^2$$ $$f(x)=-2(x^2-6x+9)-18+18$$ $$f(x)=-2(x-3)^2$$ Thus, from the form $y=a(x-h)^2+k$, the vertex is $(3,0)$ and axis of symmetry is $x=3$. Finding the $x$-intercept by setting $y=0$: $$0=-2(x-3)^2$$ $$0=x-3$$ $$x=3$$ Thus, the $x$-intercept is $(3,0)$.
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