若f(x)在[a,b ]上连续, lt (x)_(1)lt (x)_(2)lt ... lt (x)_(n)lt b(ngeqslant 3), 则在(x1,xn)内-|||-至少有一点ξ,使 (xi )=dfrac (f({x)_(1))+f((x)_(2))+... +f((x)_(n))}(n)