9.设f(x)在[a,b]上连续,在(a,b )内可导, (a)=a,-|||-且 (int )_(a)^bf(x)dx=dfrac (1)(2)((b)^2-(a)^2). 证明:(1)存在 ξ∈-|||-(a,b),使得 =f(s); (2)在(a,b)内存在与(1)中ξ-|||-相异的点n使得 '(n)=f(n)-n+1.