第5.2节 罗必达法则 5.2 l′ hospital′s rule s ppose f and g are two real f nctions which are defined in an open interval containing a real n mber a, and we wish to comp te the limit  sometimes the answer is easy. ass me that the limits of f(x) and g(x) exist as x→a, __ if m≠0, then the limit of the q otient is simply the q otient of the limits, __ this is beca se for any infinitesimal δx ≠ 0,  if l ≠ 0 and m = 0, then the limit __ does not exist, beca se when δx ≠ 0 is infinitesimal, f(a+δx) has standard part l ≠ 0 and g(a+δx) has standard part 0. b t what happens if both l and m are 0?