It is known that the sum of the first n terms of the sequence is Sn = - 3 / 2n square + 205 / 2n 1, find the general term formula, 2, find the sum of the first n terms TN

It is known that the sum of the first n terms of the sequence is Sn = - 3 / 2n square + 205 / 2n 1, find the general term formula, 2, find the sum of the first n terms TN

1.Sn= (-3/2)n2+(205/2)n
Sn-1= (-3/2)(n-1)2+(205/2)(n-1)
Sn -Sn-1= (-3/2)n2+(205/2)n-[(-3/2)(n-1)2+(205/2)(n-1)]
That is, an = 3n-101
2. When n = 1, A1 = - 98
Tn=(a1+an)*n/2=3/2n2-199/2n