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Category: | Math |

Submitted By: | shenqiang |

Fun: | (1.75) |

Difficulty: | (2.89) |

A, B and C are positive integers such that 3^A+5^B+7^C is a square number.

What is the minimum value of this square number?

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Posted by jhosek | 04/21/11 |

figured it out by trial and error but wondering if there is an explanation or mathematical formula that leads to the answer. | |

Posted by Karnage1993 | 07/24/11 |

Yes I too am wondering if there is a mathematical way to do this. I tried finding the derivative of the equation to get the minimum value that it would produce but (3^a)(ln3) + (5^b)(ln5) + (7^c)(ln7) never equals 0. Is this question truly guess and check? :( |

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