InterviewSolution
Saved Bookmarks
InterviewSolution
| 1. |
If `sum_(r=0)^(n) ((r+2)/(r+1))""^(n)C_(r)=(2^(8)-1)/(6)`. then n isA. 8B. 4C. 6D. 5 |
|
Answer» Correct Answer - D `underset(r=0)overset(n)sum((r+1)/(r+1)+(1)/(r+1)).^(n)C_(1)` `= underset(r=0)overset(n)sum.^(n)C_(r)+underset(r=0)overset(n)sum(.^(n)C_(r))/(r+1)` `= 2^(n)+(1)/(n+1).underset(r=0)overset(n)sum.^(n+1)C_(r+1)` `= 2^(n)+(2^(n+1)-1)/(n+1)` `= ((n+3)2^(n)-1)/(n+1)` `= (2^(8)-1)/(6)` `rArr n = 5` |
|