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
  1. $\left(0, \frac{1}{e}\right]$
  2. $(0, \infty)$
  3. $\left.\left[\frac{1}{e}, \infty\right)\right]_V$
  4. $\left[\frac{1}{e^2}, 1\right)$

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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