Question

Calcular a soma dos oito termos da PA (4,7,10...)

Answer 1

$\textup{Boa noite!}$
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$\mathbf{R}\Rightarrow\textit{a2-a1}\Rightarrow\textit{7-4} =\textit{3}$
$\textit{N}=\textit{8}$
$\textit{A1}=4$_________________________________________________________$\textit{An}=\textit{A1+(n-1).r}$
$\textit{A8}=\textit{4+(8-1).3}$
$\textit{A8}=\textit{4+7.3}$
$\textit{A8}=\textit{4+21}$
$\mathbf{A8}=\mathbf{25}$
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$\textit{Sn}=\frac{\mathrm{(A1+An).n} }{\mathrm{2} }$
$\textit{S8}=\frac{\mathrm{(4+25).8} }{\mathrm{2} }$
$\textit{S8}=\frac{\mathrm{29.8} }{\mathrm{2} }$
$\textit{S8}=\frac{\mathrm{232} }{\mathrm{2} }$
$\mathbf{S8}=\mathbf{116}$

$\textup{Att;Guilherme Lima}$