57)If m is a positive odd integer between 2 and 30, then m is divisible by how many different positive prime numbers?
1)m is not divisible by 3.
2)m is not divisible by 5.
条件1 我理解的是 M 只能2到30之间,那么就有5,7,11,13,17,19,23,29,这么多个prime numbers.
条件2 我理解的是 M 可以是 3,7,9,11,13,17,19,21,23,27,29 这些,21可以被3和7除, 我判断条件1完全可以,条件2 我不太确定