Question

PLEASE HELPO 25 POINTS

Answer 1

Answer:

an = 1/2 (n) (n+1)

Step-by-step explanation:

1,3,6,10,.........

3-1=2

6-3=3

Each term is different so there is no common difference.  It is not an arithmetic sequence

3/1=3

6/3 =2

Each term is different so there is no common ratio.  It is not a geometric sequence

1       3            6        10

  +2          +3          +4

a1 = 1

a2  = 3

a3 = 6 = 2*3

a4 =  10 = 2*5