the number of different prime factors of 48.和the number of different prime factors of 72
问题描述：
the number of different prime factors of 48.和the number of different prime factors of 72
答
48=（2*3）*（2*2*2）
so the number of different prime factors of 48 is 2 (only 2 and 3)
72=2*2*2*3*3
There are also two different prime factors of 72.
Hope this helps.