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What is the recursive rule for this geometric sequence? 7, 21, 63, 189, …

A. a1=7;an=3⋅an−1


B. a1=7;an=13⋅an−1


C. a1=21;an=7⋅an−1


D. a1=3;an=7⋅an−1

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Respuesta :

Answer:

A

Step-by-step explanation:

a1=7:an=3*an-1

sqdancefan

Answer:

  A. a1=7;an=3⋅an−1

Step-by-step explanation:

Clearly, the first term is 7, so a1=7.

The ratio of any term to the one before it is 21/7 = 63/21 = 189/63 = 3, so that relation is ...

  [tex]a_n=3\cdot a_{n-1}[/tex]

These values of a1 and an match the first choice.

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