Equation Icon  d d d ( 1 ) Ef ′(x ) :=---f(x ) − --ℐ [f ](x) = --- ---------f(N+1)(ξx)ωN+1 (x) dx ( dx dx) (N + 1)! ----1---- -d- (N+1) ----1---- (N+1 ) d-- = (N + 1)! dx f (ξx) ωN+1 (x) + (N + 1)!f (ξx) dxωN+1 (x). (8.10 )