问一题~

evelyn205205

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.

ANSWER: C


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.

ANSWER: C

evelyn205205

THX

zl8801

C  
because  if  you take 5,  reminder is 0, if you take 9 reminder is 8

Same trial for 2)  so,    can’t be held

now 1)+2)

Imagine, if  2 is not a factor ,3 is not a factor, so  N Can be  5, 7,11, always the prime number.  Now (n-1)(n+1)   is sure to be an even number as each is even,  n-1 can be surely divided by 4, so doest n+1   and n-1 or n+1 can be divided by 3.    so  you can get a number like 2*4*3  so that it can be divided by 24  reminder is 0

evelyn205205

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evelyn205205

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