Question
Download Solution PDFThe sum of the first 8 terms of a GP is five times the sum of its first 4 terms. If r≠1 is the common ratio, then what is the number of possible real values of r?
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFCalculation:
Given,
The sum of the first 8 terms of a GP is 5 times the sum of its first 4 terms.
The formula for the sum of the first n terms of a GP is:
Substitute for
Let x = r4, giving the quadratic equation:
Solving for x , we get:
Since x = r4, this gives:
The number of possible real values of r is two:
Hence, the correct answer is Option 2.
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