求助DATA SUFFICEINCY一题

harrycarrie

Q16:
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.
    
A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.


求助这类求余的思路

harrycarrie

这道题的答案是C，我用了反例法分别排除了A,B，但是对于两者共同存在的前提下，找不到合适的方法直接求解。跪求高人指点

lg77xx

n= 1, 2, 3, 4, 5....r都有不同的结果

harrycarrie

谢谢lg77大，可是在n同时满足两个要求的时候，r值就固定了，为0。我是想请教在同时满足两个条件的情况下，有没有除了枚举法之外的方法，可以直接求r的值