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Find the sum of n terms :- 1 2 +4 2 +7 2 +............. Question based on Sequence and series.

Find the sum of n terms :-
12+42+72+.............
Question based on Sequence and series.

Grade:11

2 Answers

Arun
25750 Points
6 years ago
its n terms will be (2n –1)2
thus Tn = 4n^2 + 1 – 4n
so Sn = \sumTn
Sn  = \sum(4n^2 + 1 – 4n)
now open sigma seperately
Sn = \sum 4n^2 + \sum 1 – \sum 4n
 
put formula and you will get the answer
 
Hope it helps
SHISHIR KUMAR PADHAN
15 Points
3 years ago
Its n term will be (3n-2)2 
So the terms can be written as,
9n2+12n+4,
S Sn = 9(12+22+32+...+n2 )+12(1+2+3+...+n)+4
= {9(n)(n+1)(2n+1)/6}+{12(n)(n+1)/2}+4
 

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