Asked by Lucina

Q.Determine the sum of each infinite geometric series.

t_1= 8 r = -2^1/2
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A.This is a divergent series because the absolute value of r is greater than 1.

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Q. The first term of an infinite geometric series is -18, and its sum is -45. Find the common ratio.
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A. I should substitute the given information into the formula for an infinite series.

-45 = 18/1-r
2.5 = 1-r
1.5 = r <---
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Thank you
Answered by Steve
Having answered #1 correctly (divergent because |r| > 1), how an you then be happy with the sum of an infinite series where r = 1.5?

-45 = -18/(1-r)
1-r = 2/5
r = 3/5
Answered by Lucina
1-r = 2/5
r= 3/5 <---- ? why add 1/5?
Answered by Steve
you're kidding, right? Remember your algebra I? I didn't add 1/5, I subtracted 2/5 from both sides, and added r to both sides!
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