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Question

Mathematics Question on Maxima and Minima

The maximum value of logexx\frac{log_ex}{x}, if x > 0 is

A

ee

B

11

C

1e\frac{1}{e}

D

1e- \frac{1}{e}

Answer

1e\frac{1}{e}

Explanation

Solution

(y=loge xx)(y = \frac{log_e \ x}{x})
?(dydx=1logexx2)? \left(\frac{dy}{dx}=\frac{1 - log_e x}{x^2}\right)

For maxima, dy/dx=0dy/dx = 0
?1logex=0? 1 - log_e x = 0
?x=e? x = e
dy/dxdy/dx changes sign from positive to negative at x=ex = e
?ymax=1/e? y_{\text{max}} = 1/e