Math, asked by ganuj31, 1 year ago

find the minimum value of x/log x

Answers

Answered by InnerWorkings
19

Answer:

Minimum value = e

Step-by-step explanation:

At local minima first derivative of function is zero and second derivative is positive.

f(x) =  \frac{x}{log(x)}  \\   \frac{dy}{dx}  =  \frac{log(x) \times 1 -  \frac{1}{x} \times x }{{( \ \log(x))}^{2} }  \\  =  \frac{log(x) - 1}{ {(log(x))}^{2} }  \\ and \: second \: derivtive \: is \\  \frac{ {d}^{2} y}{d {x}^{2} }  =  \frac{ {(log(x))}^{2}  \times  \frac{1}{x}  - (log(x) - 1) \times  \frac{2log(x)}{x} }{ {(log(x))}^{4} }

Now equate first derivative to zero

And at that point verify if second derivative is positive

 \frac{log(x) - 1}{ {(log(x))}^{2} }  = 0 \\ logx = 1 \\ i.e. \: x = e \\ at \: x = e \: second \: derivative \: is \\  =  \frac{1}{e}  > 0 \\

Therefore f (x) is minimum at x=e

Now minimum value of the function is f (e) = e/log (e) = e

Hope this helps you

Answered by patelaayushi2624
15

Answer:

the local minimum value of x/logx = e

Step-by-step explanation:

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