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5 votes
What is the sum of an 8 term geometric sequence if the first term is -11, the last term is 180,224 and the common ratio is -4

-143,231
-36,047
144,177
716,144

User Smace
by
6.3k points

1 Answer

5 votes

Answer:

3rd option

Explanation:

The sum of n terms of a geometric sequence is


S_(n) =
(a_(1)(r^(n)-1) )/(r-1)

where a₁ is the first term and r the common ratio

Here a₁ = - 11 and r = - 4 , then

S₈ =
(-11(-4)^(8)-1) )/(-4-1)

=
(-11(65536-1))/(-5)

=
(-11(65535))/(-5)

=
(-720885)/(-5)

= 144177

User Felix Yan
by
6.5k points
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