⑩天掌 Teaching Plan on Advanced Mathematics 将上两步合起来: vE>0,38>0,使当0<x-xn<时, f(u)-f(a)=fl(x)1-f(a) ∴lim∫qp(x)=∫(a)=[img(x) x→x0 x→x0 意义 1.极限符号可以与函数符号互换; 2变量代换(u=p(x)理论依据Tianjin Polytechnic University Teaching Plan on Advanced Mathematics 将上两步合起来: , 0  0,  0, 使当0 x− x 时 f (u) − f (a) = f[(x)]− f (a) lim [ ( )] ( ) 0 f x f a x x  = →  [lim ( )]. 0 x x x  → = 意义 1.极限符号可以与函数符号互换; 2.变量代换(u=(x))的理论依据