Answer:
interval is the function decreasing.
Step-by-step explanation:
Given : The graph of
is transformed to 
To find : On which interval is the function decreasing?
Solution :
First we plot the graph of both the functions,
The graph of
is shown with black line.
The graph of
is shown with violet line.
Refer the attached figure below.
The graph shows the interval over which it is increasing or decreasing.
As we notice it is increasing on the interval 
Decreasing on 
Therefore,
interval is the function decreasing.