The {an} is an equal ratio sequence composed of positive numbers, Sn is the sum of the first n terms, a2a4 = 1, S3 = 7, S5 =?

a3=1
a1*q^2=1；
S3=a1+a2+a3=a1+a1×q+1=7
q=1/2,a1=4
S5=7+1/2+1/4=31/4

Let {an} be an equal ratio sequence composed of positive numbers, and Sn be the sum of its first n terms. Given that a2a4 = 1, S3 = 7, then S5=______ ．

If the number sequence is composed of positive numbers, then q ＞ 0, and A23 = a2a4 = 1, ｜ A3 = 1 ＞ 0; and S3 = a1 + A2 + a3 = 1q2 + 1q & nbsp; + 1 = 7, that is, 6q2-q-1 = 0, then q = 12, or q = - 13 does not conform to the meaning of the problem. If it is rounded off, then an = A3 × Q (n-3) = (12) (n-3); {A1 = 4;} S5 = 4 × (1 − 125) 1 − 12 = 314

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