Question

Calcule a soma dos 100 primeiros termos da PA ( -3,2,7,...)

Answer 1

$\textup{Boa noite!}$

$\mathbf{R}\Rightarrow\textit{a2-a1}\Rightarrow\textit{2-(-3)}\Rightarrow\textit{2+3} = \textit{5}$
$\textit{N} = \textit{100}$
$\textit{A1} = -3$

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$\textit{An} = \textit{A1+(n-1).r}$
$\textit{A15} = \textit{-3+(100-1).5}$
$\textit{A15} = \textit{-3+99.5}$
$\textit{A15} = \textit{-3+495}$
$\mathbf{A15} = \mathbf{492}$
_________________________________________________________$\textit{Sn} = \frac{\mathrm{(A1+An).n} }{\mathrm{2} }$
$\textit{S15} = \frac{\mathrm{(-3+492).100} }{\mathrm{2} }$
$\textit{S15} = \frac{\mathrm{489.100} }{\mathrm{2} }$
$\textit{S15} = \frac{\mathrm{48900} }{\mathrm{2} }$
$\mathbf{S15} = \mathbf{24450}$

$\textup{Att;Guilherme Lima}$