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Culegere de probleme de Analiz˘a numeric˘a

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8.3. Alt¸i operatori liniari s¸i pozitivi 121<br />

Problema 8.3.4 (Operatorul Favard-Szasz) Fie f : [0,∞) → R astfel încât<br />

lim f(x) = 0 s¸i a > 0 fixat. Să se arate că dacă f ∈ C[0,a] operatorii Favardx→∞<br />

Szasz <strong>de</strong>finit¸i prin<br />

are proprietatea<br />

uniform pe[0,a].<br />

(Lmf)(x) =<br />

∞ (mx) k<br />

e<br />

k!<br />

−mx f<br />

k=0<br />

lim<br />

m→∞ Lmf = f<br />

Solut¸ie. Pentru funct¸iile <strong>de</strong> probă1,t,t 2 avem<br />

T.B.P.K. ⇒ concluzia.<br />

Lm(1;x) = 1<br />

Lm(t;x) = x<br />

Lm(t 2 ;x) = x 2 + x(x+1)<br />

m<br />

<br />

k<br />

m

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