Precalculus (10th Edition)

Published by Pearson
ISBN 10: 0-32197-907-9
ISBN 13: 978-0-32197-907-0

Chapter 3 - Linear and Quadratic Functions - Chapter Review - Chapter Test - Page 164: 2

Answer

The $y$-intercept is $-8$. The $x$-intercepts are $-\dfrac{4}{3}$ and $2$.

Work Step by Step

Determine the $y$-intercept by setting $x=0$ then solving for $y$: $y=f(0)=3(0^2)-2(0)-8=-8$ Thus, the $y$-intercept is $-8$. Determine the $x$-intercepts by sestting $y=0$ then solving the equation using the quadratic formula $x=\dfrac{-b\pm\sqrt{b^2-4ac}}{2a}$. $3x^2-2x-8=0$ (so $a=3, b=-2,$ and $c=-8$) $x=\dfrac{2\pm\sqrt{(-2)^2-4(3)(-8)}}{2(3)}=\dfrac{2\pm 10}{6}=\dfrac{1\pm 5}{3}$ $x_1=\dfrac{1-5}{3}=-\dfrac{4}{3}$ $x_2=\dfrac{1+5}{3}=2$ Thus, the $x$-intercepts are $-\dfrac{4}{3},2$.
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.