Maths Divisible Question ? (Urgent)
show that if a and b are positive integers and a^3 l b^3 , then a l b
回答 (4)
To jeanhim,Copestone既證明係based on a^3|b^3呢個前提,而你呢個例子並不乎合呢個前提。
不明這一句:「我們證明了任意質數 p|a 必有 p|b, 所以 a|b。 」
2 | 4 2 | 6 so 4 | 6 ??
既然要完全從基本出發,那麼 M must be a cubic root 有跳步,並不明顯。
2008-10-15 00:02:51 補充:
啊,我真白目,謝。今次錯不了。
By assumption, for some k, ka^3 = b^3.
Let GCD(a, b) = m. Then a = mc and b = md
and so kc^3 = d^3, where GCD(c, d) = 1
But then c | d^3, GCD(c, d) = 1 would imply that c = 1, and so k = d^3. As a result, da = b and so a | b. We are done.
2008-10-15 11:42:25 補充:
對不起,原先的有點亂來,不好意思。其實最重要的一步是把 a 及 b 的共同因子完全約掉,那麼剩下的因子就必定互質,就可以輕易得出結論了。
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