Sn=3n^2-2n+5
an=sn-s(n-1)
=3n^2-2n+5-[3(n-1)^2-2(n-1)+5]
=3n²-2n+5-[3n²-6n＋3-2n＋2＋5]
=6n-5
(n>1)
a1=3-2+5=6
即
an=6n-5 (n>1)
6 ,n=1