Question

Indicate a general rule for the nth term of this sequence. 12a, 15a, 18a, 21a, 24a, . . .

Answer 1

It is an arithmetic progression. Note the general rule for AP sequences:

a(n) = a(1) + (n - 1)d
a(1) = 12a (first term)
d = 3a (common difference)

General rule: a(n) = 12a + (n - 1)*3a