Intermediate Algebra (12th Edition)

Published by Pearson
ISBN 10: 0321969359
ISBN 13: 978-0-32196-935-4

Chapter 8 - Section 8.6 - More about Parabolas and Their Applications - 8.6 Exercises - Page 557: 12

Answer

$\left(\dfrac{1}{2},\dfrac{19}{4}\right)$

Work Step by Step

To find the vertex, the given function, $ f(x)=x^2-x+5 ,$ should be converted in the form $f(x)=a(x-h)^2+k$. Grouping the variables together, the given function is equivalent to \begin{align*} f(x)&=(x^2-x)+5 .\end{align*} Completing the square of the expression with variables by adding $\left(\dfrac{b}{2}\right)^2,$ the expression above is equivalent to \begin{align*} f(x)&=\left(x^2-x+\left(\dfrac{-1}{2}\right)^2\right)+\left[5-\left(\dfrac{-1}{2}\right)^2\right] \\\\ f(x)&=\left(x^2-x+\dfrac{1}{4}\right)+\left[5-\dfrac{1}{4}\right] \\\\ f(x)&=\left(x-\dfrac{1}{2}\right)^2+\left[\dfrac{20}{4}-\dfrac{1}{4}\right] \\\\ f(x)&=\left(x-\dfrac{1}{2}\right)^2+\dfrac{19}{4} .\end{align*}Note that $\left(\dfrac{b}{2}\right)^2$ should be subtracted as well to negate the addition of that value when completing the square of the expression with variables. Since the vertex of the quadratic function $f(x)=a(x-h)^2+k$ is given by $(h,k)$, then the vertex of the quadratic function above is $ \left(\dfrac{1}{2},\dfrac{19}{4}\right) $.
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