Question

Calcular a soma dos termos da p.a. (2,5,8,...,65)

Answer 1

65 = 2 +(n-1) 3
65 = 2 + 3n-3
65-2+3 = 3n
n = 66/3
n = 22

s22 = (2 + 65).22/2
s22 = 67.11
s22 = 737          ok