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: 49

Answer

General shape:

Work Step by Step

Step 2 $y'=-(x^{2}-x+2)=-(x-2)(x+1)$ $y''=-(2x-1)$ Step 3 $y'=0$ when $ x=-1,2\qquad$... critical points. Step 4 The graph of $y'$ is a parabola that opens down, so it is positive between the zeros, and negative on the other two intervals. $ \left[\begin{array}{llllllll} y': & & -- & | & ++ & | & -- & \\ & (-\infty & & -1 & & 2 & & \infty)\\ y: & & \searrow & & \nearrow & & \searrow & \end{array}\right]$ Step 5 For concavity, $y''=-(2x-1)$, $y''=0$ for $x=\displaystyle \frac{1}{2}$ $ \left[\begin{array}{ccccc} y': & & ++ & | & -- & \\ & (-\infty & & 1/2 & & \infty)\\ y: & & \cup & inf l.& \cap & \end{array}\right]$
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