It is something squared then a minus sign and then something squared, like this: . Be careful though, the "something squared" might not necessarily look like something squared. For example: could be the difference of two squares if you let and . So really it is the difference of any two expressions, i.e. expression minus expression, where each of the two expressions can reasonably be considered to be the square of some other expression.
John
My calculator said it, I believe it, that settles it
