Question

must a function that is decreasing over a given interval always be negative over that same interval explain

Answer 1

check the picture below.

notice, a function that is decreasing, namely have a negative slope, doesn't have to be negative.

Answer 2

no

Explanation:

For a function to be decreasing over an interval, the outputs on the function are getting smaller as the inputs of the function are getting larger, but the outputs could be positive or negative. For a function to be negative over an interval, the outputs must be negative, while the inputs could be positive or negative.