设公比为n,则a2=a1×n,a3=a1×n^2,a4=a1×n^3原式a1a4=27即为a1^2×n^3=27; ①a2+a3=12 即为a1×n+a1×n^2=12 ②由①可知a1=(27/n^3)^0.5 ,将a1=(27/n^3)^0.5带入等式②（等式两边开平方）可得如下等式：27n^2-90n+2...