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AP EAMCET · Maths · Application of Derivatives

If the function \(f(x)=x^3+b x^2+c x-6\) satisfies all the conditions of Rolle's theorem in \([1,3]\) and \(f^{\prime}\left(\frac{2 \sqrt{3}+1}{\sqrt{3}}\right)=0\), then \(b c=\)

  1. A \(18\)
  2. B \(-66\)
  3. C \(38\)
  4. D \(-46\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(-66\)

Step-by-step Solution

Detailed explanation

\(f(1)=f(3)\) \(1^3+b(1)^2+c(1)-6 = 3^3+b(3)^2+c(3)-6\) \(1+b+c-6 = 27+9b+3c-6\) \(b+c-5 = 9b+3c+21\) \(8b+2c = -26 \implies 4b+c=-13 \quad (1)\) \(f'(x) = 3x^2+2bx+c\) Let \(x_0 = \frac{2\sqrt{3}+1}{\sqrt{3}} = 2+\frac{1}{\sqrt{3}}\).…