HALP!!!

Let up Hugo,

this is a standard maths question that could have come from any school or text book anywhere in the world.

Hi Melody, while this may appear to be one, I perfectly recall this from being in... the lesson about "simon's favorite factoring trick" or +/- one lesson.

However I do understand that there are similar questions not property of AoPS and if I hadn't taken that particular course I would have thought it wasn't one, but I do remember having trouble with this one.

So what? 

Students all over the whole world have been having trouble with this one for over a hundred years. 

It is a completely standard question.

I do not even know why this is an AoPS question at all.  It is not problem-solving, it is a standard algebraic question.