The formula for any arithmetic sequence is an = a1 + d(n - 1), where a represents the value of the nth term, a1 represents the value of the first term, d represents the common difference, and n represents the term number. What is the formula for the sequence -15, -11, -7, ...?
an = -15 + (-4)( n - 1)
an = -15 + ( n - 1)
an = 4 + (-15)( n - 1)
an = -15 + 4( n - 1)