Question

find all intervals on which the graph of f is increasing.

Explanation:

Step1: Recall increasing - function definition

A function $y = f(x)$ is increasing on an interval if for any two points $x_1$ and $x_2$ in the interval with $x_1

Step2: Analyze the given graph

Looking at the graph of $y = f(x)$, we observe the intervals where the graph is rising.
We see that the graph is rising on the intervals $(-8,-6)$, $(0,4)$ and $(7,9)$.

Answer:

$(-8,-6),(0,4),(7,9)$