Q40 / 104 · NTA Abhyas (JEE Main) 2020 · Mathematics · Indefinite Integration

If B=∫1ex+1dx=-f(x)+C, where, C is the constant of integration and ef0=2, then the value of ef-1 is

  • A
    4
  • Correct answer
    B
    e+1
  • C
    2e
  • D
    0

Solution

The given integral is B=∫e-x1+e-xdx
Let, e-x+1=t
⇒-e-xdx=dt
∴B=∫-dtt=-ln⁡t+C
⇒B=-ln⁡e-x+1+C
∴fx=ln⁡e-x+1
Thus, ef-1=eln⁡e+1=e+1

Hence, the correct answer is option: 'B'.

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