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2014-05-31T20:28:05-03:00
Sn =  \frac{a1(q^{n} - 1)}{q - 1}  = 12285 =  \frac{3(2^{n} - 1)}{2 - 1}\\\\
2^{n} - 1 =  \frac{12285}{3}\\\\
2^{n} - 1 = 4095\\\\
2^{n} = 4096\\\\
2^{n} = 2^{12}\\\\
\boxed{n = 12}
12 termos no total
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