JEE Advanced2013MathematicsApplication of DerivativesActual
The function f x = 2 x + x + 2 - x + 2 - 2 x has a local minimum or a local maximum at x =
Options
- A- 2
- B- 2 3
- C2
- D2 3
Correct answer
A. - 2
Step-by-step solution
f x = 2 x + x + 2 - x + 2 - 2 x CASE 1: For x ≤ - 2 , x = - x and x + 2 = - x + 2 ( ∵   x ,   x + 2 < 0 ) ⇒   f ( x ) = - 3 x - 2 - x - 2 = - 3 x - 2 + ( x - 2 )   ( ∵   x - 2 < 0 ) = - 2 x - 4   . . . ( 1 ) CASE 2: For - 2 < x ≤ 0 , x = - x   ∵   x < 0   &   x + 2 = ( x + 2 )   ( ∵   x + 2 > 0 ) ⇒   f ( x ) = - 2 x + ( x + 2 ) - ( x + 2 ) + 2 x = - x + 2 - 3 x + 2 = - x + 2 + ( 3