3 years ago

Given a geometric sequence with a1=5 and a4=135 find a2.

Mathematics

1 answer:

Sergeu [11.5K]3 years ago

8 0

Answer:

Step-by-step explanation:

Terms in a geometric series that are n apart will have a ratio that is r^n. Here we have terms a4 and a1, which are 4-1=3 apart, so their ratio is ...

a4/a1 = 135/5 = 27 = r^3

r = ∛27 = 3

The second term is the first, multiplied by this common ratio:

a2 = a1·r = 3(5)

a2 = 15

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