Question

Find an equation for the nth term of the arithmetic sequence.

9, 11, 13, 15, ...

Answer Choices
A) an = 9 + 2(n - 1)
B) an = 9 + 2(n + 1)
C) an = 9 + 2
D) an = 9 + 2(n)

Answer 1

The first term is 9. The common difference is 11 -9 = 13 -11 = 2. The general term has the formula
  an = a1 + d(n-1)

Substituting the values above, you have ...
  A) an = 9 + 2(n - 1)