Given a2 = 7 and a5 = −56 of a geometric sequence, what is the recursive equation for the nth term? a an = 2(an − 1), a1 = 3.5 b an = 2(an − 1), a1 = −3.5 c an = −2(an − 1), a1 = 3.5 d an = −2(an − 1), a1 = −3.5