If sn=3n2 + n then find a16

1.	If sn=3n2 + n then find a16
Answer» Since , Sn=3n^2+n. .................1 Therefore Sn-1=3(n-1)^2+n-1. Or =3(n^2+1-2n)+n-1. Or =3n^2+3-6n+n-1. Or =3n^2-5n+2 ..............2 We know that ,. An=Sn-Sn-1. Or. =3n^2+n-(3n^2-5n+2) Or. =6n-2. Now,. A16=6(16)-2=96-2={94} Hence, 16th term of this A.P. is 94

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