Find the first three terms of the arithmetic series described.
a_1=1,a_n=19,s_n=100

1, 3, 5

Step-by-step explanation:

The sum of an arithmetic series is:

S_n = n (a_1 + a_n) / 2

100 = n (1 + 19) / 2

n = 10

The nth term of an arithmetic sequence is:

a_n = a_1 + d (n − 1)

19 = 1 + d (10 − 1)

d = 2

The common difference is 2.  So the first three terms are 1, 3, and 5.

i think it is 18

step-by-step explanation: