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Please solve RD Sharma class 12 Chapter Maxima and Minima exercise Multiple choice question, question 6 maths textbook solution.

Answers (1)

Answer:  option (b) 4 

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

Given: f(x)=x^4-x^2-2x+6

Solution:

We have,

f(x)=x^4-x^2-2x+6

f'(x)=4x^3-2x-2

f'(x)=(x-1)(4x^2+4x+2)

For maxima and minima f'(x)=0

(x-1)(4x^2+4x+2)=0

\Rightarrow x-1=0

\Rightarrow x=1

Now,

f''(x)=12x^2-2

f''(1)=12-2=10>0

So, x = 1 is a point of local minima.

The local minimum value is given by f(1)=1-1-2+6 =4

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