Question

Calcular a soma dos termos da PG ( 1, ¼, 1/16, ...).

Answer 1

PG 
an=a1.q^(n-1) 

PG infinita: 
Sn=a1/(1-q) 

a1=1 
a2=-1/4 
q=a2/a1 = (-1/4)/1 = -1/4 

Sn=1/(1-(-1/4)) = 1/(1+1/4) = 1/(5/4) =4/5 = 0,8