Question

Find the indicated sum for each sequence. S9 of –9, 36, –144, 576, ... A –585 B –471,861 C 1,887,435 D –471,852

Answer 1

-471,861

Step-by-step explanation:

Answer 2

Answer: Choice B) -471,861

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Step-by-step explanation:

This is a geometric sequence because each new term is found by multiplying the last term by -4.

The common ratio is r = -4. The first term is a = -9. We want to sum up n = 9 terms.

Use the geometric nth partial sum formula below to plug in the terms mentioned

`S_n = (a*(1-r^n))/(1-r)\\\\S_9 = (-9*(1-(-4)^9))/(1-(-4))\\\\S_9 = (-9*(1-(-262144)))/(1+4)\\\\S_9 = (-9*(1+262144))/(1+4)\\\\S_9 = (-9*(262145))/(5)\\\\S_9 = (-2359305)/(5)\\\\S_9 = -471,861\\\\`