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TS EAMCET · Maths · Application of Derivatives

The condition that \(f(x)=a x^3+b x^2+c x+d\) has no extreme value, is

  1. A \(b^2>3 a c\)
  2. B \(b^2=4 a c\)
  3. C \(b^2=3 a c\)
  4. D \(b^2 < 3 a c\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(b^2 < 3 a c\)

Step-by-step Solution

Detailed explanation

Given curve is \[ f(x)=a x^3+b x^2+c x+d \] On differentiating w.r.t. \(x\), we get \[ f^{\prime}(x)=3 a x^2+2 b x+c \] For extremum, \(f^{\prime}(x)=0\) \[ \therefore \quad 3 a x^2+2 b x+c=0 \] Since, it has no extremum value…