Question: every odd whole number can be written as the difference of two squares?
Answer: You can make every odd number by taking consecutive squares. (n+1)^2 - n^2 = 2n+1, every odd number can be written in the form 2n+1. ... Thus, a number n can only be a difference of two squares if it has two factors of the form (a + b) and (a - b), where a + b \geq \sqrt{n} and a - b \leq \sqrt{n}.