.
.
f (x), [ a, b ] (m +1) x 0, x 1, , xm: f (x 0), f (x 1), f (xm) f (x) x. . : L (x) , xi (k =0,1,, m), , f (xi), f (x), x [ a, b ] f (x)@ L (x).
. , , f (x) - .
L (x), L (xi) = f (xi) (i =0,1,, m), m - lk (x), k =0,1,, m, , , 1 x = xk 0 x = xi, i ¹ k.
1. , , , k.
lk (x). x = xi, i ¹ k lk (x)=0, :
x = xk lk (x)=1, lk (x) x = xk , :
:
, (1)
L (x)= :
(2)
L (xi) = f (xi). m L (xi)= f (xi) ; , f (x)@ L (x)- .
. lk (x) , w (x) = (x-x 0)(x-x 1) (x-xm), 0 x 0, x 1,, xm.
: (x ¹ x k)
(xk-x 0) (xk-xk -1)(xk-xk +1) (xk-xm) =
, . (3)
.
f (x)- L (x), x - [ a, b ], . , f (z) (m +1)- . , j (z)= f (z)- l (z)- Kw (z) (m +1) 0 xi (i= 0,1,, m). K , z = x j (x)=0,..
(1), ( x ¹ xi, w (x)¹0).
(m+ 1) m+ 2 x, x 0, x 1, , xm j (z) m+ 1 j' (z). j' (z) m (m+ 1) , m . , (m+ 1)- x (m+1) - j ( m +1)(z), :
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j ( m +1)(x)=0(a<x<b)(2).
L ( m +1)(z)º0 L (z) m, a w ( m +1)(z)º(m+ 1)! j (z),:
j ( m +1)(z) =f ( m +1)(z)- K (m+ 1)!
(1) , . :
(a<x<b) (3).
. f (x)@ L (x) .
: [ a, b ] , , f (x)@ L (x): .