Question:hard

If Rolle's theorem holds for the function \(f(x)=x^{3}+px^{2}+qx+5,x\in [1,3]\) with \(c=2+\frac{1}{\sqrt{3}}\), then the values of \(p\) and \(q\) are respectively...

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Use f(1) = f(3) and the fact that c is a root of f'(x).
Updated On: Nov 12, 2026
  • \(6,-11\)
  • \(6,11\)
  • \(-6,11\)
  • \(-6,-11\)
Show Solution

The Correct Option is C

Solution and Explanation

Step 1: Condition from the endpoints
$f(1)=f(3)$ gives $4p+q=-13$.

Step 2: Condition from c
The roots of $3x^2+2px+q=0$ are $2\pm\dfrac1{\sqrt3}$, so the equation is $3(x-2)^2-1=0$, i.e. $3x^2-12x+11=0$.

Step 3: Compare
Comparing $2p=-12$ and $q=11$ gives $p=-6$, $q=11$, which also satisfies $4p+q=-13$.

Final Answer:
The values are $p=-6$ and $q=11$. \[ \boxed{\text{(C) }-6,\,11} \]
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