If $f(x)=2 x^3-15 x^2-144 x-7$, then $f(x)$ is strictly decreasing in

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Aicharya · Accepted Answer

$\begin{aligned} & \mathrm{f}(\mathrm{x})=2 \mathrm{x}^3-15 \mathrm{x}^2-144 \mathrm{x}-7 \ & \mathrm{f}^{\prime}(\mathrm{x})=6 \mathrm{x}^2-30 \mathrm{x}-144 \ & 	ext { When } \mathrm{f}^{\prime}(\mathrm{x}) < 0, 	ext { we get } \mathrm{x}^2-5 \mathrm{x}-24 < 0 \ & 	herefore(\mathrm{x}-8)(\mathrm{x}+3) < 0 \Rightarrow-3 < \mathrm{x} < 8 \end{aligned}$

If $f(x)=2 x^3-15 x^2-144 x-7$, then $f(x)$ is strictly decreasing in

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