Question

ache a soma dos 35 primeiros termos da p.a (3,-2,-7,...)

Answer 1

A₃₅= A₁+34r

A₃₅= 3+34(-5)

A₃₅= 3-170

A₃₅= -167

Fórmula da soma de n termos → Sn= (A₁+A₃₅)35/2

Sn= (A₁+A₃₅)35/2

Sn= (3+(-167))35/2

Sn= (3-167)35/2

Sn= -164*35/2

Sn= -5740/2

Sn= -2870

Resposta → A soma dos 35 primeiros termos resultaram em -2870.

Answer 2

Boa noite!

Dados:

A1 → 3

N → 35

R → a2-a1 → -2-3 = -5

_______________

An=a1+(n-1)·r

a35=3+(35-1)·(-5)

a35=3+34·(-5)

a35=3-170

a35=-167

_______________

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

$\textit{S35}=\frac{\mathrm{(3+(-167).35}}{\mathrm{2}}$

$\textit{S35}=\frac{\mathrm{(3-167).35}}{\mathrm{2}}$

$\textit{S35}=\frac{\mathrm{-164.35}}{\mathrm{2}}$

$\textit{S35}=\frac{\mathrm{-5740}}{\mathrm{2}}$

$\mathbf{S35}=\boxed{-2870}$

Att;Guilherme Lima