

InterviewSolution
Saved Bookmarks
1. |
Find the sum of n terms of series ` 2.4 + 6.8 + 10.12+.....` |
Answer» when a=2,d=4 `a_n`=2+(n-1)4=4n-2 When a=4,d=4 `a_n`=4+(n-1)4=4n `T_n=(4n-2)(4n)=8[2n^2-n)` `S_n=sumT_n=sum16n^2-8n` `(16n(n+1)(2n+1))/6-(8n(n+1))/2` `(8*n(n+1))/2[(2(2n+1))/3-1]` `4n(n+1)[(4n+2-3)/3]=(4n(n+1)(4n-1))/3`. |
|