Find all pairs of integers that satisfy the equation .
Solution
Answer: where is arbitrary integer.
Solution:
If then . We now assume that .
Let and . Dividing the sides of the equation by , we get . Thus . Since and are coprime, the only possibility is and the equation reduces to
As the same integer is simultaneously a cube and a fourth power, it is a twelfth power of some integer, yielding for some integer . Substituting into the equation and taking cube root gives or, equivalently, . Since , the minus sign is not possible, therefore . We conclude that and , where is an arbitrary integer different from and . In this case and the solution satisfies the original equation. If or , we get the initial solution .
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