Write the formula for the general term of the sequence. Assume the first term of the sequence corresponds to n = 1.
9, 19, 29, 39,...
The first thing we'll do for the sequence is make a table to help us see the relationship between n and an.
Each term is 1 less than a multiple of 10. Which multiple of 10 depends on n.
The formula for the general term is an = 10n – 1.