JEE Advanced · 2010 · 11 Apr 2010 · Paper 1 · Sequences and Series

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Let , denote the sum of the infinite geometric series whose first term is and the common ratio is . Then the value of is

Answer: 3

Solution

The sum of an infinite geometric series with first term and common ratio (where ) is .

For :


Now:




This is a telescoping series:




Adding (which is negligible), the answer is 3.

JEE Advanced · 2010 · 11 Apr 2010 · Paper 1 · Integer answer

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