Question

a soma dos termos da pa (40, 70... ) ( 20 termos)​

Answer 1

r=70-40=30

An=A¹+(n-1)×r

An=40+(20-1)×30

An=40+19×30

An=40+570

An=610

Sn=(Aⁿ+A¹)×n/2

S=(610+40)×20/2

Sn=650×20/2

Sn=13000/2

Sn=6500

Answer 2

Resposta:

S20 = 6500

Explicação passo-a-passo:

PA  

a1 = 40

r = 70 - 40 = 30

an = a1 + (n - 1) . r

a20 = 40 + 19.30

a20 = 40 + 570

a20 = 610

Sn = (a1 + an).n/2

Sn = (40+610).20/2

Sn = 650.20/2

S20 = 6500