Question

determine the domain on which the following function is decreasing.

Explanation:

Step1: Identify decreasing - part of graph

A function is decreasing when as $x$ increases, $y$ decreases. Looking at the graph, the function starts to decrease after the vertex.

Step2: Locate vertex

The vertex of the parabola - like graph seems to be at $x = 4$. After $x = 4$, as $x$ increases, $y$ decreases.

Answer:

The function is decreasing on the domain $[4,9]$ (assuming the graph ends at $x = 9$).