Can someone help me with this math homework please!

It is not necessary that the function decreasing over a given interval always be negative.
A function f(x) (value) decreases as x increases.
This does not mean that value of f(x) is negative.
It can have positive number as range.
Answer:
No
Explanation:
Firstly, observe the function f(x)=-2^x, this function is decreasing and negative (below the x-axis) over its domain.
At the same time, consider the function h(x)=1-x² over the interval 0 ≤ x≤1. this function is decreasing over the said interval. However, it is not negative.
Therefore, a function doesn´t need to be negative over the interval it is decreasing on.
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Hope it helps...
Have a great day!!