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A day full of math games & activities. Find one near you.
Solution:
It is given that
f(x) = -(x + 8))2 - 1
We know that graph of f(x) is decreasing if f’(x) < 0
-(x + 8))2 - 1 < 0
-2(x + 8) < 0
x + 8 > 0
x > -8
Therefore, the graph is decreasing over [-8, ∞).
Summary:
Over [-8, ∞), the graph of f(x) = -(x + 8))2 - 1 is decreasing.