Question

Determinar o décimo segundo termo da PG (15, 30, 45, ...).
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Answer 1

$\Large\boxed{\begin{array}{l}\sf (15,30,45)\longrightarrow esta~sequ\hat encia~\acute e~uma~PA\\\sf r=30-15=15\\\sf a_{12}=a_3+9r\\\sf a_{12}=45+9\cdot15\\\sf a_{12}=45+135\\\sf a_{12}=180\end{array}}$