5. Continuity and Differentiation
medium

यदि फलन $f(x)=2 x^{3}+ b x^{2}+ c x, x \in[-1,1]$ के लिए बिंदु $x=\frac{1}{2}$ पर रोले का प्रमेय लागू होता है, तो $2 b + c$ बराबर है

A

$-3$

B

$-1$

C

$2$

D

$1$

(JEE MAIN-2015)

Solution

Conduction for Rolls theorem

$f(1)=f(-1)$

and $f^{\prime}\left(\frac{1}{2}\right)=0$

$c=-2$ and $b=\frac{1}{2}$

$2 b+c=-1$

Standard 12
Mathematics

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