4-B 证:取E 2 limf(x)=A381>090<x-x0<8时 x→y f(x)A<8 img(x)=B彐2>030<x-x<时 g(x)-b<8 4-B 4-B A-E<∫(x)<A+E→A <f(x)<A+“ 2 4-B 4-B B-E<g(x)<B+E→B g(x)<b+ 2 2 A+B 2<f(x)<A+ 4-B 4-B B 2 <g()-+B 2 A+B f(x)> 2 >g(x)即f(x)>g(x) 1010 f x A x x lim ( ) 0 g x B x x lim ( ) 0 A f (x) A B g(x) B 1 0 0 x x0 1 时 f (x) A 2 0 0 x x0 2 时 g(x) B 2 ( ) 2 A B f x A A B A 2 ( ) 2 A B g x B A B B 证: 0 2 A B 取 2 ( ) 2 A B f x A A B 即 2 ( ) 2 A B g x A B B ( ) 2 ( ) g x A B f x 即 f (x) g(x)