JEE Advanced2014MathematicsApplication of DerivativesActual
Let f : 0 , ∞ → R be given by f x = ∫ 1 x x e - t + 1 t d t t , then
Options
- Af x is monotonically increasing on 1 , ∞
- Bf x is monotonically decreasing on (0, 1)
- Cf x + f 1 x = 0 , for all x ∈ 0 , ∞
- Df 2 x is an odd function of x on R
Correct answer
A. f x is monotonically increasing on 1 , ∞
Step-by-step solution
f ′ x = 2 e - x + 1 x x Which is increasing in 1 , ∞ Also, f x + f 1 x = 0 g x = f 2 x = ∫ 2 - x 2 x e - t + 1 t t d t g - x = ∫ 2 x 2 - x e - t + 1 t t d t = - g x Hence, an odd function