Question

1- Calcule o 25 termo
(5,10,15,20,25...)
1a) A soma dos 25 primeiros termos
URGENTE

Answer 1

P.A.(5,10,15,20,25,,.....)

a 1 = 5

a 2 = 10

r = a 2 - a 1

r = 10 - 5

r = 5

a 25 = a 1 + (n - 1 ).r

a25 = 5 + (25 - 1 ).5

a25 = 5 + 24 . 5

a25 = 5 + 120

a25 = 125

Sn = n . (a1 + an) / 2

S25 = 25 . (5 + 125) / 2

S25 = 25.(130)/2

S25 = 3250 / 2

S25 = 1625