2. The square difference between two odd numbers can be divisible by 8.

3. Let two odd numbers be 2a+ 1, 2b+ 1, and A and B are integers.

(2a+ 1)^2-(2b+ 1)^2

=(2a+ 1+2 b+ 1)(2a+ 1-2 B- 1)

=2(a+b+ 1)*2(a-b)

=4(a+b+ 1)(a-b)

(1) When both A and B are even or odd, there are: a-b is even, let a-b=2k, and k is an integer.

(2a+ 1)^2-(2b+ 1)^2

=8k(a+b+ 1) is a multiple of 8.

(b) when a and b are odd and even.

A+b+ 1 is an even number, so a+b+ 1=2k'

(2a+ 1)^2-(2b+ 1)^2=8k'(a-b)

To sum up: (2a+ 1) 2-(2b+ 1) 2 is a multiple of 8, which means it can be divisible by 8.