Whoops, might not have been clear enough. In more mathy terms: Multiplication by 2 means "1 (starting point) times 2 (scaling)" If we "do the opposite" we can

Whoops, might not have been clear enough. In more mathy terms: Multiplication by 2 means "1 (starting point) times 2 (scaling)" If we "do the opposite" we can take the inverse of the starting point or the scaling: -1 (additive inverse of starting point) times 2 = -2 or reverse the operation 1 (same starting point) * 1/2 (scaling inverse) = 1/2 Of course, we assume the scaling term is what's being inverted, but it's important to think about the meaning. There's a hidden parameter for these operations and sometimes making it explicit can be helpful. (I.e., euler's formula, e^ix, is better seen as 1.0 * e^ix. That is, you are starting at 1.0 then doing a rotation.)