Answer:
Let's define.
If the graph is above the x-axis, then it is positive.
if the graph is below the x-axis, then it is negative.
if the graph is going up, then it is increasing.
if the graph is going down, then it is decreasing.
And notice that this graph is only valuable in the interval (-9, 10) outside that segment, the graph diverges to infinity or minus infinity, so we should only analyze the graph in that segment.
A: Interval over which the difference of the numbers of sales is negative.
Easily we can see that the region is: (-3, 10)
B: Interval over which the difference of the numbers of sales is increasing
We can see that it starts increasing around x = 5, and keeps increasing after that, then the correct option is (4.9, 10)
C: interval over which the difference of the numbers of sales 15 positive:
(i suppose that 15 = is)
We can see that the graph is positive between x = -9 and x = -3, the correct option is (-9, -3)
D: Interval over which the difference of the numbers of tale decreasing.
The graph starts to decrease around x = -6, and it starts to increase in x = 4.9.
Then the correct option here is: (-6.3, 4.9) (this option is not given but the decreasing segment is this one.
