# Chapter 5 - Graphs and the Derivative - 5.1 Increasing and Decreasing Functions - 5.1 Exercises - Page 260: 9

a) $(-\infty,-1)$ & $(3,\infty)$ b) $(-1,3)$

#### Work Step by Step

Step 1: Graphically find the values where $f'(x)$ is equal to $0$, positive & negative. Step 2: $f(x)$ is increasing where $f'(x)$ is positive. Step 3: $f(x)$ is decreasing where $f'(x)$ is negative. Note: The answer is in interval notation.

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