Find the intervals in which `f(x)=-x^2-2x+15` is increasing or decreasing.

Explanation

To find the intervals in which the function \( f(x) = -x^2 - 2x + 15 \) is increasing or decreasing, we will follow these steps:

### Step 1: Find the derivative of the function
To determine where the function is increasing or decreasing, we first need to find the derivative \( f'(x) \).

\[ f(x) = -x^2 - 2x + 15 \]
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