NTA Abhyas JEE Main2020MathematicsIndefinite IntegrationPractice
If B = ∫ 1 e x + 1 d x = - f ( x ) + C , where, C is the constant of integration and e f 0 = 2 , then the value of e f - 1 is
Options
- A4
- Be + 1
- C2 e
- D0
Correct answer
B. e + 1
Step-by-step solution
The given integral is B = ∫ e - x 1 + e - x d x Let, e - x + 1 = t ⇒ - e - x d x = d t ∴ B = ∫ - d t t = - ln t + C ⇒ B = - ln e - x + 1 + C ∴ f x = ln e - x + 1 Thus, e f - 1 = e ln e + 1 = e + 1