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imc

number theory intermediate

Problem

How many ordered pairs of positive integers, with , have the property that their squares differ by ?
(A)
(B)
(C)
(D)
Solution
Find all of the factor pairs of : You can eliminate and ( because you cannot have two numbers add to be an even number and have an odd difference at the same time without them being a decimal. You only have pairs left, so the answer is .
Final answer
B