Three conditions. \r\n 1 Both numerator and denominator tend to be zero or infinite. \r\n 2 Both the numerator and denominator can be derived in the centripetal neighborhood of the value that the variable tends to. \ r \ n3After the numerator and denominator are differentiated respectively, the ratio exists or tends to infinity. \r\n L 'Bida's law (L'H? Pital's rule is a method to determine the uncertainty under certain conditions by taking the derivative and limit of the numerator and denominator respectively. The French mathematician L'H?pital (Marquis de l'H? Pital) published this rule in his book Analysis of Curves des Infinitesimal Analysis in 1696, so it was named after him. But it is generally believed that this rule was first discovered by Swiss mathematician johann bernoulli, so it is also called Bernoulli rule.