2另两种情形: 1.x→-0情形:limf(x)=A x→-0 vE>0,X>0,使当x<-X时,恒有f(x)-A<6 2x→∞情形:mf(x)=A vE>0,丑X>0,使当|xX时,恒有f(x)-A<E 定理:limf(x)=A分limf(x)=A且lim∫(x)=A x→0 x→+0. x →  情形 : 0 2   0, X  0,使当| x | X时,恒有 f (x) − A   . . x → − 情形 : 0 1 f x A x = →− lim ( )   0,X  0,使当x  −X时,恒有 f ( x ) − A   . lim f x A x = → ( ) 2.另两种情形: 定理:lim x→ f (x) = A  lim f (x) A lim f (x) A. x x = = →+  且 →− 