JEE Main2015MathematicsApplication of DerivativesActual
Let k and K be the minimum and the maximum values of the function f x = 1 + x 0.6 1 + x 0.6 in 0 , 1 , respectively, then the ordered pair ( k , K ) is equal to:
Options
- A2 - 0.4 , 1
- B2 - 0.6 , 1
- C2 - 0.4 , 2 0.6
- D1,2 0.6
Correct answer
A. 2 - 0.4 , 1
Step-by-step solution
f x =   1 + x 0.6 1 + x 0.6 f ′ x =   0.6 1 + x - 0.4   1 + x 0.6 - 0.6   x 0.4 1 + x 0.6 1 + x 0.6 2 = 0.6   1 + x - 0.4   1 + x 0.6 - x - 0.4   1 + x 2 1 + x 0.6 2 = 0.6 x 0.4 - 1 1 + x 0.4 1 + x 0.6 2 Clearly it is always negative in [ 0 ,   1 ] minimum value would be at x = 1 . ( 1 + 1 ) 0.6 1 + 1 0.6 =   2 0.6 2 = 2 - 0.4 = k & maximum values would be at x = 0 ( 1 + 0 ) 0.6 1 + 0 0.6 = 1 1 = K Hence 2 - 0.4 , 1