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QJEEM13Ma9bab: JEE Main 2013 Mathematics - Class 12 JEEM13Ma9bab Solution: The real number for which the equation, has two distinct real…

The real number kk for which the equation, 2x3+3x+k=02{x^3} + 3x + k = 0 has two distinct real roots in [0, 1]\left[ {0,\,1} \right]

Multiple Choice Options

  • A lies between 1 and 2
  • B lies between 2 and 3
  • C lies between −1- 1 and 0
  • D does not exist.

Step-by-Step Verified Solution

f(x)=2x3+3x+kf\left( x \right) = 2{x^3} + 3x + k

f'\left( x \right) = 6{x^2} + 3 > 0

∀x∈R\forall x \in R       \,\,\,\,\,\, (as       \,\,\,\,\,\, {x^2} > 0 )

⇒f(x)\Rightarrow f\left( x \right) is strictly increasing function

⇒f(x)=0\Rightarrow f\left( x \right) = 0 has only one real root, so two roots are not possible.

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