Don’t try to memorize the formulas as they are presented in the books. Instead, re-arrange the formulas; it makes them much easier to understand and memorize. More details are here:
http://www.ryharv.com/2011/06/the-easy-way-to-remember-all-the-free-cash...
http://www.ryharv.com/2011/06/the-easy-way-to-remember-all-the-free-cash...