Question

ache a soma dos termos da p.a (-35,-28,...,2912)

Answer 1

Boa noite!

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Dados;

A1 → -35

An → 2912

N → ?

R → a2-a1 → -25-(-35) → -25+35 = 7

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An=a1+(n-1)·r

2912=-35+(n-1)·7

2912=-35+7n-7

2912-7n=-35-7

-7n=-42

n=-42/-7

n=6

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$\textit{Sn}=\frac{\mathrm{(A1+An).n}}{\mathrm{2}}$

$\textit{S6}=\frac{\mathrm{(-35+2912).6}}{\mathrm{2}}$

$\textit{S6}=\frac{\mathrm{2877.6}}{\mathrm{2}}$

$\textit{S6}=\frac{\mathrm{17262}}{\mathrm{2}}$

$\mathbf{S6}=\boxed{8631}$

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Att;Guilherme Lima