Sn = [n2(n+1)2] /4



ii.
Sn
=
n2(n+1)2











4








Sol.
Sn
=
n2(n+1)2











4








S1
=
12(1+1)2
=
1(2)2
=
1×4
=
4
=
1



4

4

4

4














S2
=
22(2+1)2
=
4(3)2
=
4×9
=
36
=
9



4

4

4

4














S3
=
32(3+1)2
=
9(4)2
=
9×16
=
9×4
=
36



4

4

4





We know that,
t1 = S1 = 1
t2 = S2 – S1 = 9 – 1 = 8

t3 = S3 – S2 = 36 – 9 = 27


The first three terms of the sequence are 1, 8 and 27.