Question If x^3+y^3=z^3 has a solution in integers x, y, z, show that one of the three must be a multiple of 7. How should I solve this question? Thank you very much.

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Originally Posted by Jenny20 Question If x^3+y^3=z^3 has a solution in integers x, y, z, show that one of the three must be a multiple of 7. How should I solve this question? Thank you very much. Work modulo 7. Possibilities, We assume . In that case not all can be multiple of sevens. The possibilities that do not lead to contradiction, We see a multiple of seven does exist.

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