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1,3la puterea n+1,3la puterea n+1+2×1,3la puterean+2=5,×1,69la puterea 4

Răspuns :

1,3^n + 1,3^(n+1) + 2·1,3^(n+2) = 5·1.3^8   
1,3^n ·(1 + 1,3 + 2·1,69) = 5·1,3^8
1,3^n ·5,68 = 5·1,3^8
daca 1,3^n ·5,68 = 5,68·1,3^8 ⇒
⇒  n = 8
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