等比数列前n项乘积为tn,且2a3=a4的平方,求t9

等比数列前n项乘积为tn,且2a3=a4的平方,求t9

an=a1q^(n-1)
2a3=(a4)^2
2a1.q^2 = (a1)^2 .q^6
a1q^2( a1q^4 -2 ) =0
a1q^4=2
Tn= a1.a2.an
= (a1)^n .q^[n(n-1)/2]
n=9
T9=(a1)^9 .q^36
= (a1.q^4)^9
=2^9
=512