b-a 由h a+hj=0,1,22…,n AHx,=a+ih, x=a+th, dx= hdt x-x1=(t-i)h,x1-x=(j-1)h x=a时t=0;x=b时t=n。 因此 bamx二x=m工二m ∏ I(t-i)dt        =  =  =  = − − = − − = − − − = = = = = − = − − = − = + = + = = + = − = n n i j i n i j i n n i j i b a n i j i j i n i j i j i i j t i dt n j i hdt j i t i nh dx x x x x b a C x a t x b t n x x t i h x x j i h x a ih x a t h dx hdt x a j h j n n b a h 0 0 0 0 0 0 ( ) ( ) 1 1 1 1 0; ( ) , ( ) , , , , 0,1,2,..., 因此 时 时 。 知 ， 由