两个质数的和差积商一定都还是质数吗？

解答如下：

两个质数的和、差不一定还是质数。如：11-2=9【合数】，7-5=2【质数】，13+2=15【合数】，15+2=17【质数】

两个质数的积一定不是质数！如：2×3=6【合数】，3×5=15【合数】，因为得到的数的因数除了1和本身，还有这两个质数，所以得到的数一定是合数，一定不是质数。

两个质数的商一定不是质数！如：5÷2=2.5，5÷3=5/3，得到的商不是整数，所以不可能是质数。

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