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The Minimum Value of X Loge X is Equal to (A) E (B) 1/E (C) − 1/E (D) 2/E (E) − E - CBSE (Science) Class 12 - Mathematics

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Question

The minimum value of x loge x is equal to ____________ .

  • e

  • `1/e`

  • `-1/e`

  • `2/e`

  • `-e`

Solution

\[\frac{- 1}{e}\]

 

\[\text { Here }, \]

\[f\left( x \right) = x \log_e x\]

\[ \Rightarrow f'\left( x \right) = \log_e x + 1\]

\[\text { For a local maxima or a local minima, we must have } \]

\[f'\left( x \right) = 0\]

\[ \Rightarrow \log_e x + 1 = 0\]

\[ \Rightarrow \log_e x = - 1\]

\[ \Rightarrow x = e^{- 1} \]

\[\text { Now,} \]

\[f''\left( x \right) = \frac{1}{x}\]

\[ \Rightarrow f''\left( e^{- 1} \right) = e > 0\]

\[\text { So,} x = e^{- 1}\text {  is a local minima }. \]

\[\text { Hence, the minimum value of } f\left( x \right) = f\left( e^{- 1} \right) . \]

\[ \Rightarrow e^{- 1} \log_e \left( e^{- 1} \right) = - e^{- 1} = \frac{- 1}{e}\]

  Is there an error in this question or solution?

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Solution The Minimum Value of X Loge X is Equal to (A) E (B) 1/E (C) − 1/E (D) 2/E (E) − E Concept: Graph of Maxima and Minima.
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