The least positive integer n for which \sqrt{n+1}-\sqrt{n-1}

KVPY SA Exam 2013 Question Paper

Question : 12 of 80

Marks: +1, -0

The least positive integer n for which

√{n+1}-√{n-1} < 0.2

Solution:

√{n+1}-√{n-1} < 0.2

squaring

1.96 < 0.4 √{n-1}

again squaring

(4.9)^2 + 1 < n

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