If A3 = 3, A9 = 75, then a10=______ ．

If A3 = 3, A9 = 75, then a10=______ ．

Let the common ratio of the equal ratio sequence be q, then a9a3 = a1q8a1q2 = Q6 = 753 = 25, that is, Q3 = ± 5, the solution is q = ± 35, so A10 = a9q = ± 7535

It is known that the equal ratio sequence {an} is an increasing sequence, and a5a7 = 32, A3 + A9 = 18, then calculate a10

Because it is an equal ratio sequence, A3 * A9 = A5 * A7 = 32, joint A3 + A9 = 18
The solution is A3 = 16, A9 = 2 or A9 = 16, A3 = 2
But an is increasing, so it can only be A9 = 16, A3 = 2
Common ratio Q ^ 6 = A9 / A3 = 8
Positive root q = root 2
A10 = Q * A9 = 16 * radical 2

In the equal ratio sequence {an}, if A6 = 6, A9 = 9, then A3 is ()
A. 4B. 32C. 169D. 2

∵ A3 = a1q2, A6 = a1q5, A9 = a1q8, ∵ a3a9 = (A6) 2, A3 = a62a9 = 629 = 4