623 - A block - due Thursday 14.11.20

finish chpt 13.1 - arithmetic series

SUM FORMULA:

S = (n / 2)(t₁ +t_n)

TERM FORMULA:

 t_n -  t₁ = d(n - 1)

n = number of terms
t_n = last term or nth term
t₁ = first term
d = difference