Question

calcule a soma dos 25 primeiros termos da P.A (1;3;5;...)

Answer 1

razão = 3-1 = 2
a1 = 1
n = 25
an = 1+(25-1)*r
an = 1+25*2
an = 51
Sn = (a1+an)*n/2
Sn = (1+51)*25/2
Sn = 52*25/2
Sn = 26*25
Sn = 650