任取x2>x1>-1/4f(x2)-f(x1)=(3-x2)/(4x2+1)-(3-x1)/(4x1+1)=((3-x2)(4x1+1)-(3-x1)(4x2+1))/(4x2+1)(4x1+1)=(12x1+3-4x1x2-x2-12x2-3+4x1x2+x1)/(4x1+1)(4x2+1)=13(x1-x2)/(4x1+1)(4x2+1)x1-x20,4x2+1>0f(x2)-ff(x1)...