99 Percentile Qs Bank for JEE MainMathematicsDefinite Integration
The value of x > 1 satisfying the equation ∫ 1 x t log ⁡ t d t = 1 4 , is
Options
- Ae
- Be 3 2
- Ce 2
- D2 e - 1
Correct answer
A. e
Step-by-step solution
Consider that, I = ∫ 1 x t log t d t = log t ⋅ t 2 2 1 x - ∫ 1 x 1 t ⋅ t 2 2 d t = x 2 2 log x - 1 2 t 2 2 1 x = x 2 2 log x - 1 2 x 2 2 - 1 2 ⇒ 1 4 = x 2 2 log x - 1 4 x 2 - 1 ⇒ 1 2 x 2 log x - 1 4 x 2 = 0 (as x > 1 ) ⇒ x 2 2 log x - 1 = 0 ⇒ 2 log x - 1 = 0 ⇒ log x = 1 2 ⇒ x = e 1 2 ⇒ x = e