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Geometric sequences.

Geometric sequences.-example-1
User Drobati
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1 Answer

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a1 = 9/20

a6 = 8/135

an = a1 . q^(n - 1)

a6 = a1 . q^5

8/135 = 9/20 . q^5

q^5 = 8/135 . 20/9

q^5 = 160/1215

q = 2/3

Now let's multiply a1 by it a couple times.

a1 = 9/20

a2 = 9/20 . 2/3 = 18/60 = 3/10

a3 = 3/10 . 2/3 = 6/30 = 3/15

a4 = 3/15 . 2/3 = 6/45 = 2/15

a5 = 2/15 . 2/3 = 4/45

a6 = 4/45 . 2/3 = 8/135

The only ones that appear on the alternatives are 4/45, 2/15 and 3/10.

User Sabof
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