Respostas

2014-03-17T21:26:23-03:00
An = A1 + (n-1).r
A20 = 2 + 19x2
A20 = 40

Soma = [(A1 + A2) . n] / 2
Soma = [(2 + 40) . 20] / 2
Soma = 420.
2 2 2