A 
First thought it might be E. But then only noticed its n^2 minus 1 !! he he
First thought it might be E. But then only noticed its n^2 minus 1 !! he he Looking forward to 2013 MBA admissions!
The only exception to this is 1. But that won't trouble the answer in any way, because in that case, the product will be 0 - (1-1)*(1+1) = 0 thus choice A will hold true.Ian Stewart wrote:You might notice that this is a difference of squares:zagcollins wrote:If n is a positive integer and r is the remainder when n^2-1 is divided by 8, what is the value of r?
1)n is odd
2)n is not divisible by 8
n^2 - 1 = (n+1)(n-1)
If n is odd, then n-1 and n+1 are consecutive even integers. If you take any two consecutive even integers, one of them will be divisible by 4, the other not, so their product must be divisible by 8. Thus, if we know n is odd, we can be certain that n^2 -1 will be divisible by 8, and r will be zero. 1) is sufficient. 2) is not; n might be even, or might be odd. A.
