Question 575092
It all depends, but it takes practice. For example,


*[tex \LARGE x^2 - 49]


is obviously a difference of two squares. So is


*[tex \LARGE 4x^4 - 16y^{10}].


However, something like


*[tex \LARGE (a+b+c)(a-b+c)] might tempt one to expand the whole thing, when it is indeed a difference of squares, and can be expressed as


*[tex \LARGE (a+c)^2 - b^2].