The first T-shirt you buy costs $7, and every additional shirt costs only $5. Let f (n) be the total cost of n shirts. F is a sequence. What kind of sequence is it?

f (n) = 2 + 5n. This is an arithmetic sequence.

Step-by-step explanation:

f (1) = 7

f (2) = 7 + 5

f (3) = 7 + 5 + 5 = 7 + 10

f (4) = 7 + 5 + 5 + 5 = 7 + 15

In general,

f (n) = 7 + 5 (n - 1)

= 7 + 5n - 5

= 2 + 5n

We have the sequence 7, 12, 17, 22, 27 ...

This is an arithmetic sequence, because it is a sequence of numbers in which the common difference between consecutive terms is 5.