若∫8(x)d=0则由上式知∫f(x)g(x)dx=0 →∫/(x)g(xk=/)s(x)可取l内任一点 a b b 若∫x)则g(xd>0(xg(x →n≤ M 由介值定理 f(x)g(x)dx g(r)dx 彐5∈|a,使f(5)=b g(x)dx f(x)g(x dx=f(5 g(x)d若 ( ) = 0  b a g x dx 则由上式知  = b a f (x)g(x)dx 0    = b a b a f (x)g(x)dx f ( ) g(x)dx  可取[a ,b]内任一点 若     b a b a g(x)dx 0,则 g(x)dx 0 M g x dx f x g x dx m b a b a      ( ) ( ) ( ) 由介值定理     = b a b a g x dx f x g x dx a b f ( ) ( ) ( )  [ , ] 使 ( )    = b a b a f (x)g(x)dx f ( ) g(x)dx