NTA Abhyas JEE Main2020MathematicsDeterminantsPractice
If A r = 1 r r + 1 1 3 r 2 3 , then lim n → ∞ ∑ r = 1 n A r is equal to
Options
- A0
- B2
- C4
- D8
Correct answer
B. 2
Step-by-step solution
A r = 1 r r + 1 1 3 r 2 3 = 1 r - 1 r + 1 1 3 r 2 3 ⇒ lim n → ∞ ⁡ ∑ r = 1 n A r = 1 - 1 2 + 1 2 - 1 3 + 1 3 - 1 4 + …     1 3 + 1 3 2 + 1 3 3 + … 2 3 = 1     1 3 1 - 1 3 2 3 = 1 1 2 2 3 = 3 - 1 = 2