ratio of partial sums of the same geometric sequence
My kid was given this question:
In a geometric sequence, the proportion of (the sum of the first
terms) to (the sum of the first terms) is . Find the common ratio of the sequence.
The only formula thus far covered for the partial sum of a geometric sequence
The solution I found is as follows, but it seems too roundabout for the context, so I wonder what more direct way there is:
The given information means
1 answer
I think your approach is the expected one, but a shortcut if rigour is not required would be to note that the absolute value of the ratio must be greater than 1, or the proportion couldn't exceed
(Of course, this doesn't exclude other solutions: see "if rigour is not required" above).
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