Answer:
(–∞, 0)
Explanation:
The graph of the absolute value parent function f(x) = |x| is shown in the attached diagram.
We can clearly see that from -∞ to 0, the function is decreasing and from 0 to +∞, it is increasing. This is the basic, parent absolute value function.
THe questions asks, when is it decreasing, so clearly, it is from -∞ to 0.
This is the answer.