Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 2 - Section 2.2 - Quadratic Functions - Exercise Set - Page 332: 81

Answer

\[\left( 3,\ -1 \right)\]

Work Step by Step

We know that parabolas always have a lowest point. This point, where the parabola changes direction, is called the `vertex'. If the quadratic is written in the form $y=a{{\left( x-h \right)}^{2}}+k,$ then the vertex is the point $\left( h,\ k \right)$. For a given $y=a{{x}^{2}}+bx+c\,,$ the vertex $\left( h,\ k \right)$ is found by computing $h=\frac{-b}{2a},$ and then equation $y$ at $h$ to find $k.$ If you have already learned the quadratic formula, you may find it for $k,$ since it is related to both the formula for $h$ and the discriminant in the quadratic formula: $k=\frac{\left( 4ac-{{b}^{2}} \right)}{4a}.$ By equating the coefficients $a,$ $b,$ and $c,$ that is $a=1\,\,\,\,\,\,\,\,b=-6\,\,\,\,\,\,\,\,c=8$ The formula for the vertex gives $h=\frac{-b}{2a}=\frac{-\left( -6 \right)}{2\left( 1 \right)}=3$ Then we can find $k$ by equating $y$ at $h=3$ $\begin{align} & k=\frac{\left( 4ac-{{b}^{2}} \right)}{4a} \\ & =\frac{\left( 4\times 1\times 8 \right)-{{\left( -6 \right)}^{2}}}{4\times 1} \\ & =-1 \\ \end{align}$ Hence, the vertex of the parabola is $\left( 3,-1 \right).$
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.