Find the first five terms and the fifth partial sum of the sequence whose nth term is an=n2-3n.

Question

Find the first five terms and the fifth partial sum of the sequence whose n^th term is a_n=n²-3n.

Answer 1

an = n^2 - 3n

a1 = 1-3 = -2

a2 = 4-6 = -2

a3 = 9-9 = 0

a4 = 16-12 = 4

a5 = 25-15 = 10

s5 = -2-2+0+4+10 = 10