Question

Find the first Tow terms of the seqence Sn=n2(n+1)

Answer 1

S1 = 2(1+1)

=2×2

=4

a=4

S2 =2×2(2+1)

=4×3

=12

n/2(2a+(n-1)d)=12

2/2(8+d)=12

8+d=12

d=4

a2 =a+d

=4+4

8

first two terms are 4 and 8