NTA Abhyas JEE Main2020MathematicsDefinite IntegrationPractice
Let the function F be defined as F x ⁡ = ∫ 1 x   e t t dt ,  x ⁡ > 0 , then the value of the integral ∫ 1 x ⁡ e t t + a dt , where a > 0 , is
Options
- Ae a F x - F 1 + a
- Be - a F x + a - F a
- Ce a F x + a - F 1 + a
- De - a F x + a - F 1 + a
Correct answer
D. e - a F x + a - F 1 + a
Step-by-step solution
F x = ∫ 1 x e t t dt I = ∫ 1 x e t t + a dt Let, t + a = y ⇒ dt = dy Also, t = 1 ⇒ y = 1 + a and t = x ⇒ y = x + a ∴ I = ∫ 1 + a x + a e y - a y dy = e - a ∫ 1 + a x + a e y y dy = e - a ∫ 1 + a x + a e t t dt = e - a F x + a - F 1 + a