PREP-1-159

lulud

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) n is not divisible by 2.



(2) n is not divisible by 3.


請問為什麼兩個條件加在一起就可以解出來了呢？