1. The problem statement, all variables and given/known data I have stumbled upon the following equation on wikipedia http://upload.wikimedia.org/math/b/8/d/b8de8bfcdf40f1793e7b72755161d61f.png To clarify, I am not sure how to simplify the equation of the form x^2/(1-x) = 1/(x^2 - x^-2) as demonstrated in the second line of the equation. 3. The attempt at a solution I temporarily reciprocated the equation to become (1-x)/ x^2 = (x^2 - x^-2) But, 1/x2 - x/x2 ≠ (x2 - x-2) ...? Something is terribly wrong here. Please advice.