University Calculus: Early Transcendentals (3rd Edition)

Published by Pearson
ISBN 10: 0321999584
ISBN 13: 978-0-32199-958-0

Chapter 4 - Section 4.4 - Concavity and Curve Sketching - Exercises - Page 239: 16

Answer

The curve, observing from left to right, - falls on $(-\infty,-1)$, is concave up, - at $(-1,1)$ changes concavity to "down" (inflection point), - and contiunes to fall on the interval $(-1,\infty)$, concave down. - (crosses the the x-axis at the origin) No extrema; inflection point at $(-1,1)$.

Work Step by Step

$y=f(x)=1-(x+1)^{3}$ $f'(x)=-3( x+1)^{2}$ $f''(x)=-6( x+1)$ Analyzing $f'(x)$, we see that it is defined everywhere, and has zeros $ x=2\qquad$... (critical point) $f'$ is always negative or 0, so $f$ is always falling $f$ has no extrema $f''(x)=0$ for $x=-1,\qquad f(-1)=1,\quad(-1,1)$ is a point of inflection. For graphing purposes: $ f(0)=0,\qquad$ Concavity and points of inflection: $\left[\begin{array}{cccccc} f''(x): & -\infty & ++ & -1 & -- & \infty & \\ f(x): & & \cup & inf. & \cap & & \end{array}\right]$
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