Function $f(x) = x^x,x>0$ decreases on the interval |
$(0,\frac{1}{e})$ $(0, e)$ $(\frac{1}{e},∞)$ $(e,∞)$ |
$(0,\frac{1}{e})$ |
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 $(0,\frac{1}{e})$ |