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  • Need solution for RD Sharma maths class 12 chapter Maxima and Minima exercise Multiple Choice question, question 21.

Need solution for RD Sharma maths class 12 chapter Maxima and Minima exercise Multiple Choice question, question 21.

Answers (1)

Answer: option(d) None of these

Hint: For local maxima or minima, we must have f'(x)=0.

Given: f(x)=x+\frac{1}{x}

Solution:

We have,

f(x)=x+\frac{1}{x}                                              

f'(x)=1-\frac{1}{x^2}                       

For maxima and minima f'(x)=0

\Rightarrow 1-\frac{1}{x^2}=0

\Rightarrow x^2-1=0

\Rightarrow x^2=1

\Rightarrow x=\pm 1

\Rightarrow x= 1(x>0)

Now,

f''(x)=\frac{2}{x^3}

f''(1)=\frac{2}{1^3}=2>0

So, x = 1 is a local minima.

Posted by

infoexpert24

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