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The interval in which the function, f(x)=7−4x−x2f(x) = 7 - 4x - x^2 is strictly increasing is

Solution

✅ Correct Option: 3

f′(x)=−4−2xf'(x) = -4 - 2x. For strictly increasing: f′(x)>0⇒−4−2x>0⇒x<−2f'(x) > 0 \Rightarrow -4 - 2x > 0 \Rightarrow x < -2. So the function is strictly increasing on (−∞,−2)(-\infty, -2).

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