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smc

algebra senior

Problem

Let , , and be positive integers with such that and . What is ?
(A)
(B)
(C)
(D)
(E)
Solution
Add the two equations. . Now, this can be rearranged and factored. , , and are all integers, so the three terms on the left side of the equation must all be perfect squares. We see that the only is possibility is . , since is the biggest difference. It is impossible to determine by inspection whether or , or whether or . We want to solve for , so take the two cases and solve them each for an expression in terms of . Our two cases are or . Plug these values into one of the original equations to see if we can get an integer for . , after some algebra, simplifies to . is not divisible by , so is not an integer. The other case gives , which simplifies to . Thus, and the answer is .
Final answer
E