Question

Calcule a soma aos 12 primeiros termos da PA(2,5,8, ...)?

Answer 1

(2,5,8,11,14,17,20,23,26,29,32,35)= 222

Answer 2

A12= 2+(12-1).3
A12= 2+11.3
A12= 35

Sn=(a1+an).n/2
S12=(2+35).12/2
S12=37.12/2
S12=444/2
S12=222