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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A

Step-by-step explanation:

a1=7:an=3*an-1

  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 ...

These values of a1 and an match the first choice.

do you mean add both of the equations together

because if you do the answer is 10x-5

step-by-step explanation:

b.my answer is b.

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