Answer:
If graph of any function going towards down in a particular interval. Then , function is decreasing in that interval.
From x = -∞ to x = a , function is positive and decreasing.
Here, a graph is attached in the question.
We know that, if graph of any function is going towards down in particular interval. Then function is decreasing in that particular interval.
If graph of any function is going towards up in particular interval. Then function is increasing in that particular interval.
In given graph. it is observed that in interval x = -∞ to x = a , graph of function is above x - axis and graph is going towards down. Therefore, in given interval function is positive and decreasing.
Explanation: