The number of the positive integer pairs (x, y) such that 1x+1y=12007 where x < y is
A
5
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B
6
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C
7
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D
8
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Solution
The correct option is C 7 1x+1y=12007⇒(x+y)2007=xy⇒xy−2007x−2007y=0(x−2007)(y−2007)=20072=34×2232 The number of pairs is equal to the number of divisors of 20072 that is (4+1)×(2+1)=15 Since so required number of pairs = 7