Question

Sn=n×n (n+1).Hence the 2nd term of AP will be ___

Answer 1

By finding An for n=3

S3=3*3(3+1). S2 = 2*2(2+1)

=3*3(4). = 2*2(3)

= 15 = 8


tn =Sn -Sn-1........formula

For n=3

t2= S3 -S3-1

= S3-S2

= 15-8

= 7


The second term is 7

Answer 2

Answer:

Sn = n*n(n+1)

so we take n = 1

S1= 1*1(1+1)

S1= 1(2)

S1=2

a=2

now we take

S2 = 2*2(2+1)

S2= 4(3)

S2= 12

WE KNOW THAT S2-S1 =a2

so

12-2 =a2

10= a2