Progression (Sequence and Series)Hard
Question
For the series S = 1 + 
(1 + 2)2 + 
(1 + 2 + 3)2 +
(1 + 2 + 3 + 4)2 +.....
(1 + 2)2 + (1 + 2 + 3)2 +(1 + 2 + 3 + 4)2 +.....Options
A.7th term is 16
B.7th term is 18
C.sum of first 10th terms is
D.sum of first 10th term is
Solution
S = 1 + 
(1 + 2)2 + 
(1 + 2 + 3)2 + 
(1 + 2 + 3 + 4)2 + ....
rth term Tr =
= (1 + 2 ...... + r)2
∴ T7 = 16
ans S10 =
Tr
=
+ (10)(10 + 1) + 10
(1 + 2)2 + (1 + 2 + 3)2 + (1 + 2 + 3 + 4)2 + ....rth term Tr =
= (1 + 2 ...... + r)2∴ T7 = 16
ans S10 =
Tr=
+ (10)(10 + 1) + 10Create a free account to view solution
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