In a geometric sequence ana_nan, if a1+a2=3a_1 + a_2 = 3a1+a2=3 and a3+a4=12a_3 + a_4 = 12a3+a4=12, what is the common ratio rrr?
r=2r = 2r=2
r=−2r = -2r=−2
r=4r = 4r=4
r=−4r = -4r=−4