What are the first three terms of the sequence:

a1=3 and an=2(an-1)^2

a)2,6,12,14
b)2,8,18
c)3,18,648
d)3,32,50

Three numbers x, y, and z are in the ratio 2: 7: 8. if 12 is subtracted from y, then three numbers form a geometric sequence (in the order x, y–12, z). find x, y, and z. there are 2 sets.