1. **Problem statement:** Determine all intervals on which the graph of the function $f$ is decreasing. 2. **Understanding decreasing intervals:** A function $f$ is decreasing on an interval if for any two points $x_1$ and $x_2$ in that interval, whenever $x_1 < x_2$, we have $f(x_1) > f(x_2)$. 3. **Given information:** The graph intersects the x-axis at approximately $x = -7$, $x = -2$, and $x = 5$. 4. **From the graph description:** The function decreases on the intervals $(-9, -7)$ and $(2, 5)$. 5. **Answer:** The function $f$ is decreasing on the intervals $$(-9, -7) \text{ and } (2, 5).$$