Mathematics · Application of Derivatives

JEE Main 2024 — 6 April, Shift 1 — Question 14

The interval in which the function f(x)=xx,x>0f(x)=x^{x}, x>0, is strictly increasing is

  1. Option A:

    (0,1e]\left(0, \frac{1}{\mathrm{e}}\right]

  2. Option B:

    [1e2,1)\left[\frac{1}{\mathrm{e}^{2}}, 1\right)

  3. Option C:

    (0,∞)(0, \infty)

  4. Option D:

    [1e,∞)\left[\frac{1}{\mathrm{e}}, \infty\right)

    Correct

Answer: D

Step-by-step solution

f(x)=xx;x>0\mathrm{f}(\mathrm{x})=\mathrm{x}^{\mathrm{x}} ; \mathrm{x}>0 ℓny=xln⁡x\ell n y=x \ln x

1ydydx=xx+ln⁡x\frac{1}{y} \frac{d y}{d x}=\frac{x}{x}+\ln x

dydx=xx(1+ln⁡x)\frac{d y}{d x}=x^{x}(1+\ln x)

for strictly increasing

dydx≥0⇒xx(1+ℓnx)≥0\frac{d y}{d x} \geq 0 \Rightarrow x^{x}(1+\ell n x) \geq 0

⇒ln⁡x≥−1\Rightarrow \ln \mathrm{x} \geq-1

x≥e−1x \geq e^{-1}

x≥1e\mathrm{x} \geq \frac{1}{\mathrm{e}}

x∈[1e,∞)\mathrm{x} \in\left[\frac{1}{\mathrm{e}}, \infty\right)

Answer key and solution verified before publishing.

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Exam
JEE Main 2024
Subject
Mathematics
Chapter
Application of Derivatives
Topic
Monotonicity
The interval in which the function f(x)=x x , x 0 , is strictly… | JEE Main 2024 PYQ with Solution · DhiX AI