Question

Enter a recursive rule for the geometric sequence. 5, −10, 20, −40, ...
a1=
an=

Answer 1

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Answer:

• a[1] = 5
• a[n] = -2a[n-1]

Explanation:

The first term is the first one on the list:

a[1] = 5

__

The ratio of terms is ...

-10/5 = -2

That is, each term is -2 times the previous one, so the recursive rule is ...

a[n] = -2·a[n-1]