PP-T2-DS-Q122

[aqboy[origen]]

122.

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.

ANS:C

請教一下~

[sunnyblue13s]

請問在哪邊遇到了思考難處?

[aqboy[origen]]

遇到"餘數"型的題目都不太會解, 不知道怎麼思考@@