Function $f(x) = x^x,x>0$ decreases on the interval
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → $(0,\frac{1}{e})$
Given: $f(x) = x^{x},\; x > 0$
Take $\log$ on both sides: $\ln f = x\ln x$
Differentiate w.r.t. $x$:
$\frac{f'(x)}{f(x)} = \ln x + 1$
$\Rightarrow f'(x) = x^{x}(\ln x + 1)$
$f'(x) < 0 \Rightarrow \ln x + 1 < 0 \Rightarrow \ln x < -1 \Rightarrow x < e^{-1}$
Hence, $f(x)$ decreases on $(0,\frac{1}{e})$