Question

 If Sn = 3n ² + 9n then its 6th term is​

Answer 1

Answer:

Given Sn=3n2+5n

S1=a1=3(1)2+5(1)=3+5=8

S2=a1+a2=3(2)2+5(2)=3(4)+10=22

⇒8+a2=22

⇒a2=14

S3=a1+a2+a3=3(3)2+5(3)=27+15=42

⇒a3=S3−S2=42−22=20

d=a2−a1=a3−a2=