#mathematics #polynomials #precalculus
Since the two factors are different by \2b\, the factors will always have the same parity. That is, if \(a-b\) is even then \(a+b\) must also be even, so the product is divisible by four. Or neither are divisible by 2, so the product is odd. This implies that numbers which are multiple of 2 but not 4 cannot be expressed as the difference of 2 squares.