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KC 2Q13: Integers

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Source: — Data Sufficiency |

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by Anurag@Gurome » Mon Feb 21, 2011 8:41 pm
n^2 + 1 means "1" added to the perfect square of an integer. Definitely, a and b will not be perfect squares. But if 1 is subtracted from a and b then they will be perfect squares always.

From the given options only in 3rd option, 1 is being subtracted from a and b, which for sure implies that √(a - 1)(b -1) should be an integer.
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