Culegere de probleme de Analiz˘a numeric˘a
Culegere de probleme de Analiz˘a numeric˘a
Culegere de probleme de Analiz˘a numeric˘a
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
124 Aproximarea funct¸ionalelor liniare<br />
f(x3) = 1<br />
h4<br />
[−f(x0)+6f(x1)−18f(x2)+10f(x3)+3f(x4)]−<br />
12h 20 f(5) (ξ3)<br />
f(x4) = 1<br />
h4<br />
[3f(x0)−16f(x1)+36f(x2)−48f(x3)+25f(x4)]+<br />
124 4 f(5) (ξ4)<br />
Problema 9.1.2 Să se construiască o formulă <strong>de</strong> forma<br />
cu gradul <strong>de</strong> exactitater = 2.<br />
Solut¸ie. ⎧ ⎨<br />
Restul cu Peano x0 < x1<br />
f ′ (α) = A0f(x0)+A1f(x1)+(Rf)(α)<br />
⎩<br />
A0 +A1 = 0<br />
A0x0 +A1x1 = 1<br />
A0x2 0 +A1x2 1 = 2α<br />
⇒ A1 = −A0 =<br />
(Rf)(α) =<br />
x1 = 2α−x0<br />
x1<br />
x0<br />
1<br />
2(α−x0)<br />
K2(s)f ′′′ (s)ds<br />
K1(s) = (α−s)+ − (x1 −s) 2<br />
4(α−x0) =<br />
<br />
1 (s−x0)<br />
= −<br />
4(α−x0)<br />
2 s ≤ α<br />
(x1 −s) 2 ≤ 0<br />
s > α<br />
K2(s) ≤ 0, s ∈ [x0,x1], α > x0, f ∈ C 3 (x0,x1)<br />
(Rf)(α) = f ′′′ (ξ)<br />
x1<br />
x0<br />
2 (α−x0)<br />
K2(s)ds = −<br />
6<br />
f ′′′ (ξ ′ )<br />
f ′ 1<br />
(α−2)2<br />
(α) = − [2f(2α−2)−f(2)]− f<br />
2(α−2) 6<br />
′′′ (ξ)<br />
λ ∈ R, λ = α, α = x0 +x1<br />
2<br />
S-a obt¸inut o familie <strong>de</strong> formule <strong>de</strong> <strong>de</strong>rivare numerică.<br />
Problema 9.1.3 Arătat¸i că<br />
f ′′ (x0) = 1<br />
h 2[f(x0 −h)−2f(x0)+f(x0 +h)]− h2<br />
12 f(4) (ξ)<br />
un<strong>de</strong>f ∈ C 4 [x0 −h,x0 +h], ξ ∈ (x0 −h,x0 +h)