Algebra 1

Published by Prentice Hall
ISBN 10: 0133500403
ISBN 13: 978-0-13350-040-0

Chapter 9 - Quadratic Functions and Equations - 9-2 Quadratic Functions - Practice and Problem-Solving Exercises - Page 545: 21

Answer

Axis of symmetry: x=2 Vertex: (2, 17) The graph is shown below:
1516851650

Work Step by Step

$y = -2x^{2} + 8x + 9$ The standard form for a quadratic equation is $y = ax^{2} + bx + c$ So a= -2, b= 8, and c= 9 Axis of symmetry: The formula for axis of symmetry is $x= \frac{-b}{2a}$ $x= \frac{-(8)}{2(-2)}$ $x= \frac{-8}{-4}$ x=2 Vertex: Plug in the x value of the axis of symmetry to find the y value of the vertex. $y = -2x^{2} + 8x + 9$ $y = -2(2)^{2} + 8(2) + 9$ y= -8 + 16 + 9 y= 17 The vertex is (2, 17) We plot the vertex on the graph. Since the a value is -2 and is negative the parabola opens downwards. So we graph a parabola starting from the vertex opening downwards.
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.