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最佳答案:做一下因子分解N^2-1=(N-1)(N+1)280=2^3*5*7显然N必须是奇数才可能满足条件N-1和N+1中恰有一个是4的倍数, 另一个除以4余2, 所以
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最佳答案:How to Keep HealthyNowadays more and more people are concerned about their healt