对于lim┬(x→4)〖(3-√(5+x))/(1-√(5-x))〗 分子分母均同乘以〖(3+√(5+x))(1+√(5-x))〗 得到lim┬(x→4)〖(3-√(5+x))/(1-√(5-x))〗= lim┬(x→4)〖-(1+√(5-x))/(3+√(5+x))〗= -2/6=-1/3（其中约去了x-4和4-x...