The formula for any geometric sequence is a n = a 1 · r n - 1, where a n represents the value of the nth term, a 1 represents the value of the first term, r represents the common ratio, and n represents the term number. what is the formula for the sequence -3, -6, -12, -24, an = -3 · 2n - 1 an = -3 · (-2)n - 1 an = 2 · (-3)n - 1 an = -2 · (-3)n - 1