Question

Given the recursive formula for the arithmetic sequence a_1=−5, a_n=a_n−1+4, find the first three terms of the sequence.

Answer 1

a1 = −5
a2 = a1 + 4 = −5 + 4 = −1
a3 = a2 + 4 = −1 + 4 = 3

So the first three terms are −5, −1, 3.