Thomas' Calculus 13th Edition

Published by Pearson
ISBN 10: 0-32187-896-5
ISBN 13: 978-0-32187-896-0

Chapter 4: Applications of Derivatives - Section 4.4 - Concavity and Curve Sketching - Exercises 4.4 - Page 213: 15

Answer

The graph, observing from left to right, - rises on $(-\infty,2)$ , is concave down, - rising, crosses the y-xis at $(0,-7)$, - still rising, crosses the x-axis at $(1,0)$ - at $(2,1)$ changes concavity to "up" (inflection point), - and contiunes to rise on the interval $(2,\infty)$, concave up. No extrema; inflection point at $(2,1)$.

Work Step by Step

$y=f(x)=(x-2)^{3}+1$ $f'(x)=3( x-2)^{2}$ $f''(x)=6( x-2)$ Analyzing $f'(x)$, we see that it is defined everywhere, and has zeros $ x=2\qquad$... (critical point) $f'$ is nonnegative, so $f$ is always rising. $f $has no extrema $f''(x)=0$ for $x=2,\qquad f(2)=1,\quad(2,1)$ is a point of inflection. For graphing purposes: $f(0)=-7,\qquad f(1)=0$ Concavity and points of inflection: $\left[\begin{array}{lllllll} f''(x): & -\infty & -- & 2 & ++ & \infty & \\ f(x): & & \cap & inf. & \cup & & \end{array}\right]$ All these data help us describe the flow of the graph, as given in the answer.
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