I'm reading a textbook that does a couple of algebraic manipulations in one step (in order to get the expressions ready for the binomial theorem). I'm unfamiliar with this step. Could anyone expand it into several steps? It's using some kind of algebraic standard technique or result that I don't know. Here's the first one: (x + dx) ^ -2 becomes x ^ -2 (1 + dx / x) ^ -2 The second one is: (x + dx) ^ 0.5 becomes x ^ 0.5 (1 + dx / x) ^ 0.5 Am I correct in inferring that there's a general rule: (a + b) ^ c becomes a ^ c (1 + b / a) ^ c If so, is there a name for this rule, and are there any conditions on the values of a, b and c for it to work?