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The interval in which the function f(x)=−x2−2x+18f(x) = -x^2 - 2x + 18 is decreasing is :

Solution

✅ Correct Option: 3

Here f′(x)=−2x−2f'(x)=-2x-2, which is negative when x>−1x>-1. Hence the function decreases on (−1,∞)(-1,\infty).

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