JEE Mains · Maths · STD 12 - 5. continuity and differentiation
If the Rolle's theorem holds for the function \(f(x) = 2x^3 + ax^2 + bx\) in the interval \([-1, 1 ]\) for the point \(c = \frac{1}{2}\) , then the value of \(2a + b\) is
- A \(1\)
- B \(-1\)
- C \(2\)
- D \(-2\)
Answer & Solution
Correct Answer
(B) \(-1\)
Step-by-step Solution
Detailed explanation
\(f\left( x \right) = 2{x^3} + a{x^2} + bx\) let, \(a=-1,b=1\) Given that \(f\left( x \right)\) satisfy Roll theorem in interval \([-1,1]\) \(f\left( x \right)\) must satify two conditions. \((1)f(a)=f(b)\) \((2)f'(c)=0\) (\(c\) should be between \(a\) and \(b\) )…
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