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Mathematics 7 Online
OpenStudy (anonymous):

i need help really fast

OpenStudy (marissalovescats):

With?

OpenStudy (anonymous):

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

OpenStudy (anonymous):

i need an answer

OpenStudy (solomonzelman):

\(\LARGE\color{midnightblue}{ \rm S_n=\frac{a_1(1-r^n)}{1-r} }\)

OpenStudy (anonymous):

) -143,231 B) -36,047 C) 144,177 D) 716,144

OpenStudy (marissalovescats):

There is a formula for it in which you plug the numbers in to find your sum And that is it^

OpenStudy (solomonzelman):

You don't need the answer, you need to get a grip on this.

OpenStudy (solomonzelman):

\(\LARGE\color{midnightblue}{ \rm S_8=\frac{(-11)(1-(-4)^8)}{1-(-4)} }\)

OpenStudy (marissalovescats):

Where a1 is the first term n is the number of numbers in the series (AKA 8) and r is the ratio

OpenStudy (anonymous):

i got -144,181.4

OpenStudy (solomonzelman):

correct. close. I got 144,177, and it is POSITIVE.

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