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Question

if an A.P sn=3n2+5nfindA.P?

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Solution

Solution :-
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=S3S2=4222=20

d=a2a1=a3a2=148=2014=6

The terms of an A.P are 8,14,20

with common difference 6

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