Download the app

Questions  

Sum of the series r=1nr2+1(r!) is

 

Remember concepts with our Masterclasses.

80k Users
60 mins Expert Faculty Ask Questions
a
(n+1)!
b
(n+2)!−1
c
n(n+1)!
d
none of these

Ready to Test Your Skills?

Check Your Performance Today with our Free Mock Tests used by Toppers!

detailed solution

Correct option is C

We can writer2+1=(r+2)(r+1)−3(r+1)+2Thus ∑r=1n r2+1(r!)=∑r=1n [(r+2)(r+1)−(r+1)−2{(r+1)−1}]r! =∑r=1n [(r+2)!−(r+1)!]−2∑r=1n {(r+1)!−r!}=(n+2)!−2!−2{(n+1)!−1}=n(n+1)!


Similar Questions

Let Sn=r=1nr!;(n>6). Then, Sn7Sn7  (where, [ . ] denotes greatest integer function) is equal to


whats app icon
phone icon