99 Percentile Qs Bank for JEE MainMathematicsDefinite Integration
Evaluate ∫ a b x x d x ,   a < b
Options
- Aa - b
- Bb + a
- Cb - a
- DN o n e o f t h e s e
Correct answer
C. b - a
Step-by-step solution
Let, I = ∫ a b x x d x We have, x x = 1 x > 0 - 1 x < 0 Case I : When 0 < a < b ⇒ I = ∫ a b 1 .   d x = x a b = b - a = b - a .......(i) Case II: When a < 0 < b I = ∫ a 0 x x d x + ∫ 0 b x x d x ⇒ I = -   ∫ a 0 1 . d x + ∫ 0 b 1 . d x = - 0 - a + b - 0 = b + a = b - | a | .......(ii) Case III : When a < b < 0 ⇒ I = ∫ a b - 1 . d x = - b - a = - b + a = b - a .......(iii) It is clear from (i), (ii) and (iii) we get ∫ a b x x   d