Question

Write an explicit formula for an, the nth term of the sequence 1, 11, 21

Answer 1

an = 10n - 9.

Explanation:

This is arithmetic with first term a1 = 1 and common difference 10.

an = a1 + d(n-1)

= 1 + 10(n - 1)

= 1 + 10n - 10

= 10n - 9.