Calculus: Early Transcendentals 8th Edition

Published by Cengage Learning
ISBN 10: 1285741552
ISBN 13: 978-1-28574-155-0

Chapter 4 - Section 4.1 - Maximum and Minimum Values - 4.1 Exercises - Page 284: 61

Answer

The absolute maximum is $f(1) = ln(3)$ The absolute minimum is $f(-\frac{1}{2}) = ln(\frac{3}{4})$

Work Step by Step

$f(x) = ln~(x^2+x+1)$ We can find the points when $f'(x) = 0$: $f(x) = ln~(x^2+x+1)$ $f'(x) = \frac{2x+1}{x^2+x+1} = 0$ $2x+1 = 0$ $x = -\frac{1}{2}$ We can find the value of $f(-\frac{1}{2})$ and the values of the function at the endpoints of the interval $[-1, 1]$: $f(-\frac{1}{2}) =ln~[(-\frac{1}{2})^2+(-\frac{1}{2})+1] = ln(\frac{3}{4})$ $f(-1) =ln~[(-1)^2+(-1)+1] = ln(1)$ $f(1) =ln~[(1)^2+(1)+1] = ln(3)$ The absolute maximum is $f(1) = ln(3)$ The absolute minimum is $f(-\frac{1}{2}) = ln(\frac{3}{4})$
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