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counting and probability intermediate
Problem
If and , for how many ordered pairs of integers is an integer?
Solution
If is an integer, then its square is also an integer. Therefore, is an integer. In other words, must be a perfect square. If we define , then the problem has asked us to find the number of ordered pairs for which , , and is a perfect square. We check the 6 possibilities for separately. If , then is 3 or 8. If , then is 2 or 7. If , then is 1 or 6. If , then , and if , then . Finally, if , then is either 10 or 3. Altogether, there are ordered pairs satisfying the given conditions.
Final answer
10