a1+a1*q=12,--->a1*(1+q)=12,
(a1q²)²=1,
若a1q²=1,则12q²-q-1=0,q=1/3, a1=9;或q=-1/4,a1=16.
若a1q²=-1,则12q²+q+1=0,无实数解