SOLUTION: Find the sum of the first 4 terms of the geometric series where t3 = -81 and r = 3.

SOLUTION: Find the sum of the first 4 terms of the geometric series where t3 = -81 and r = 3.

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Question 758153: Find the sum of the first 4 terms of the geometric series where t3 = -81 and r = 3.

Answer by josgarithmetic(39618) (Show Source): You can put this solution on YOUR website!
Sequence: , , , ,...

Now you can find the first four terms and find their sum.

-9, -9*3, -9*3*3, -9*3*3*3
sum:
= and there is a formula if you want it, but even without,
=
=
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