The interval in which the function $f(x)=x^x, x>0$, is strictly increasing is
The interval in which the function $f(x)=x^x, x>0$, is strictly increasing is
- $\left(0, \frac{1}{e}\right]$
- $(0, \infty)$
- $\left.\left[\frac{1}{e}, \infty\right)\right]_V$
- $\left[\frac{1}{e^2}, 1\right)$
Solution
$\begin{aligned}
& \mathrm{f}(\mathrm{x})=\mathrm{x}^{\mathrm{x}} ; \mathrm{x}>0 \\
& \ell \operatorname{nn}=\mathrm{x} \ell \mathrm{n} \mathrm{x} \\
& \frac{1}{\mathrm{y}} \frac{\mathrm{dy}}{\mathrm{dx}}=\frac{\mathrm{x}}{\mathrm{x}}+\ln \mathrm{n} \\
& \frac{\mathrm{dy}}{\mathrm{dx}}=\mathrm{x}^{\mathrm{x}}(1+\ell \mathrm{n} x)
\end{aligned}$
for strictly increasing
$\begin{aligned}
& \frac{d y}{d x} \geq 0 \Rightarrow x^x(1+\ell n x) \geq 0 \\
& \Rightarrow \ell n x \geq-1
\end{aligned}$
$\begin{aligned} & x \geq e^{-1} \\ & x \geq \frac{1}{e} \\ & x \in\left[\frac{1}{e}, \infty\right)\end{aligned}$
Asked in: JEE Main 2024 (06 Apr Shift 1)
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