-
Find the sum of n terms of the given series. 1.2.4 +2.3.5 + 3.4.6 + ...
-
- n(n + 1) (n + 2)
- [n(n + 1) / 12] (3n2 + 19n + 26)
- [(n + 1) (n + 2) (n + 3)] / 4
- (n2(n + 1) (n + 2) (n + 3) / 3
Correct Option: B
Put n = 1, now the sum of the series = 1.2.4 = 8
Put n = 1, in the options
(a) 1(1 + 1) (1 + 2) = 6
(b) 1(1 + 1)/12 x (3 + 19 + 26) = 8
(c) (1 + 1) (1 + 2) (1 + 3)/4 = 6
(d) 1(1 + 1) (1 + 2) (1 + 3 )/3 = 8
As, the sum of series = 8
Hence, option (a) and (c) can be rejected.
Now, put n = 2
Sum 1. 2. 4 + 2 . 3 . 5 = 38
Put n = 2, in option (b)
2(2 + 1)/12 (3 x 4 + 19 x 2 + 26)38
Hence, (b) is the correct option.
