如图。
设F(x)=f(x-1/3)-f(x)+1/3 F(1/3)=f(0)-f(1/3)+1/3=-f(1/3)+1/3 F(2/3)=f(1/3)-f(2/3)+1/3 F(1)=f(2/3)-f(1)+1/3=f(2/3)-2/3 F(1/3)+F(2/3)=-f(2/3)+2/3 ,由介值性定理,至少存在a,(1/3《a《2/3),使: F(a)=(F(1/3)+F(2/3))/2=(-f(2/3)+2/3)/2 故...