fully expand your equations, c^2 = 49 * a^2

来源: mondayadvisor 于 2015-10-17 12:14:15 [] [旧帖] [给我悄悄话] 阅读数 : (290 bytes)
回答: Thanks 由 dr_yin 于 2015-10-17 10:57:34

your soultion is correct and good  for training math research skill, but it is hard to do it in a contest with the time limit. Too many places can commit errors.

also, d is zero comes from 3rd order term in your expansion. No need to prove it by contradiction.

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• Thanks. -dr_yin- ♂ 给 dr_yin 发送悄悄话 (0 bytes) () 10/17/2015 postreply 16:18:24

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