The real number $x$ when added to its inverse gives the minimum value of the sum at $x$ equal to
The real number $x$ when added to its inverse gives the minimum value of the sum at $x$ equal to
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$-2$
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2
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1
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$-1$
Solution
$y=x+\frac{1}{x} \text { or } \frac{d y}{d x}=1-\frac{1}{x^2}$
For $\max$. or $\min ., 1-\frac{1}{x^2}=0 \Rightarrow x=\pm 1$
$\frac{\mathrm{d}^2 \mathrm{y}}{\mathrm{dx}^2}=\frac{2}{\mathrm{x}^3} \Rightarrow\left(\frac{\mathrm{d}^2 \mathrm{y}}{\mathrm{dx}^2}\right)_{\mathrm{x}=2}=2(+$ ve minima)
Therefore $x=1$
Asked in: JEE Main 2003
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