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The first and the last term of a geometric progression is equal to -8 and 1 respectively.

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the first and the last term of a geometric progression is equal to -8 and 1 respectively. If the sum of all the terms is -5, find the number of terms.
asked Apr 24, 2014 in ALGEBRA 2 by anonymous

1 Answer

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First term of the geometric progression (a ) = - 8.

Last term of the geometric progressin  image.

Substitute a = - 8 in image.

image.

Sum of geometric progression image.

Substitute a = - 8 and image in image.

image

image

image

image

image.

To find n, substitute the value r = - 1 / 2 in image.

image

image

 

n = 4.

Therefore, the number of terms of the geometric progression is 4.

answered Apr 26, 2014 by lilly Expert

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