求助两道数学题

anggie1900

数学比较差,谢谢哦~~~

If M is the least common multiple of 90, 196, and 300, which of the following is NOT a factor of M?

A.  600

B. 700

C. 900

D. 2100

E. 4900

DS 题

If n is a positive integer and r is the remainder when (n-1)(n+1) is divided by 24, what is the value of r?

 1). 2 is not a factor of n.

 2). 3 is not a factor of n.

janegon

90=2x5x3x3

196=2x2x7x7

300=2x2x5x5x3

the least common multiple = 2x2x3x3x5x5x7x7

600=2x2x2x3x5x5 (需要3个2），答案应该是A

 

anggie1900

thanks thanks~~~~~~