Question

An arithmetic sequence is given below.

Answer 1

Step-by-step explanation:

an arithmetic sequence means that any term is the result of the previous term + something.

a1 = 17

then we see that every term is the previous term -4.

a2 = a1 - 4

a3 = a2 - 4 = a1 - 4 - 4 = a1 - 8

so, we see

an = an-1 - 4

an = a1 - 4×(n-1)