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TS EAMCET · Maths · Application of Derivatives

If the function \(f(x)=x^3+a x^2+b x+40\) satisfies the conditions of Rolle's theorem on the interval \([-5,4]\) and \(-5,4\) are two roots of the equation \(f(x)=0\), then one of the values of c as stated in that theorem is

  1. A 3
  2. B \(\frac{1+\sqrt{67}}{3}\)
  3. C \(\frac{1+\sqrt{65}}{3}\)
  4. D -2
Verified Solution

Answer & Solution

Correct Answer

(B) \(\frac{1+\sqrt{67}}{3}\)

Step-by-step Solution

Detailed explanation

\(\begin{aligned} & \text { } f(x)=x^3+a x^2+b x+40 \\ & \Rightarrow 5 a-b=17...(i) \\ & \Rightarrow 4 a+b=-26....(ii) \end{aligned}\) ...(i) \([\because f(-5)=0]\) ...(ii) \([\because f(4)=0]\) From (i) and (ii), \(a=-1, b=-22\)…