ningIngelanieSchri ningIngelanieSchri

12-01-2017
Mathematics

contestada

The first term of a geometric sequence is -2 and the multiplier, or ratio, is -3. what is the sum of the first 5 terms of the sequence?
a. 162
b. 122
c. -122
d. -162

Respuesta :

MissPhiladelphia MissPhiladelphia

20-01-2017

To determine the sum of the sequence, we can finfd the first five terms however it would be tedious. Instead, we can find the sum by the expression:

S(n) = a(1) ( 1 - r^n) / 1-r
S(5) = -2 (1 - (-3)^5) / 1-5
S(9) = 122 <------------OPTION B

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