∴a 1a3=a？ 2
∫a 1 a3 = 6 a2
∴a？ 2=6a2
That is, a2(a2-6)=0
Solution: a2=6 or a2=0 (irrelevant, omitted)
∫a 1, a2, A3-80 into arithmetic progression.
∴a 1+a3-8=2a2= 12
That is a2/q+a2q=20.
∴6/q+6q=20
To simplify: 3q? - 10q+3=0
That is, (3q- 1)(q-3)=0.
Solution: q=3 or 1/3 (not suitable for the problem, omitted)
∴a 1=a2/q=6/3=2
The general formula of {an} is: an = a1q (n-1) = 2 * 3 (n-1).
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