Question

(URGENTE)
calcule a soma dos 20 termos da P.G. (1,2,3,...)

Answer 1

an=a1+(n-1).r
a20= 1+(20-1). 1
a20= 1+19.1
a20= 1+19
a20=20

Sn= (a1+an).n/2
S20= (1+20).20/2
S20= 21.20/2
S20=420/2
S20=210