Expand $(a-b)^3$ without formulas When I solve $(a-b)^2$ I take $aa-ab-ab+bb$ I do not use formulas at all because I only forget them. To solve the above example all i do is to multiply one variable or constant at the time but when I ask anyone or anything how to solve $(a-b)^3$ all they tell me is to use this or that formula etc... And I hate formulas because I only forget them. I want to learn how to calculate math not how to use math formulas. Since no one so far can answer my question I am now turning my hope to you.
How do I calculate $(a-b)^3$ without formulas? I am supposed to do $aaa+a(-2)(-2)$ and so on or what?
I really appreciate all the help I can get, thanks!

Arrange $(a-b)^3$ as $(a-b)(a-b)(a-b)$. Now sum over all ways of picking either $a$ or $-b$ from each factor. So you get 
$$aaa+(-b)aa+a(-b)a+aa(-b)+(-b)(-b)a+(-b)a(-b)+a(-b)(-b)+(-b)(-b)(-b)$$
