Question

Find a formula for the nth term in

this arithmetic sequence:
a1 = 28, 22 = 21, a3 = 14, 24 = 7, ...
an = -7n + [?]

Answer 1

answer: an = -7n + 35

Answer 2

a1 = 28

a2 = 21

common difference (d) = a2-a1 = 21-28 = -7

Therefore, an = a1+(n-1)d

= 28+(n-1)(-7) = 28-7n+7 = 35-7n

ANSEER : 35