Care este al cincilea nr din sirul:
1 ; 4; 10; 28; ...

Răspunsul a fost dat de: USER6515
2 September 2025 matematica 5 minute
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Clasă: Education Materie: matematica
Care este al cincilea nr din sirul:
1 ; 4; 10; 28; ...
Întrebare a fost pusă de:
70 Vezi 70 Răspunsuri

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Răspuns:

Explicație pas cu pas:

Fiecare termen al sirului, incepand de la al treilea, este dublul sumei celor doi anteriori lui:

a3=2(a1+a2)

a4=2(a2+a3)

..............................

an=2(an-2+an-1)

Sa verificam:

10=2(1+4)=2×5=10

28=2(10+4)=2×14=28. Da, este corect.

Atunci urmatorul termen va fi:

a5=2(28+10)=2×38=76

a5=76

Răspunsul a fost dat în data 2 September 2025

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