determine all intervals on which the graph of f is decreasing on the closed interval -9,9.

Answer:

$[-9, - 4]\cup[2,7]$

Explanation:

Step1: Recall decreasing - graph property

A function $y = f(x)$ is decreasing when as $x$ increases, $y$ decreases.

Step2: Observe the graph

On the given graph of $y = f(x)$ in the interval $[-9,9]$, we see that the function is decreasing from $x=-9$ to $x = - 4$ and from $x = 2$ to $x=7$.

Step3: Write the intervals

We use closed - interval notation since the problem asks for the closed interval $[-9,9]$. The intervals are $[-9, - 4]$ and $[2,7]$, and we combine them using the union symbol $\cup$.