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Progresia geometrica b1=2 , b2=6. Calculati b3, b4, b5, S5

Răspuns :

ratia q=b2/b1=6/2=3
b3=q*b2=3*6=18
b4=q*b3=3*18=54
b5=q*b4=3*54=162

S5=b1+b2+b3+b4+b5=2(3^5 - 1) : (3-1) = 3^5  -  1 = 243-1 = 242
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Succes!