After learning the Gas law, that I got some general idea of the beauty of equations, I think the expression of textbooks is pretty strange, they trying to divide one simple formula to several different unclear ones, hmm… I think the better the equation is the more factors it includes in; it does not let the question become complicated but even make it even simpler because people do not need to think about do they include some factors or not, so which even help them understand the concept better.