Resposta :
a1=1
razão=1-4=3
n=18
an=a1+(n-1).r
a18=1+(18-1).3
a18=1+17.3
a18=1+51
a18=52
sn=(a1+a18).n/2
s18=(1+52).18/2
s18=53.18/2
s18=954/2
s18=477
razão=1-4=3
n=18
an=a1+(n-1).r
a18=1+(18-1).3
a18=1+17.3
a18=1+51
a18=52
sn=(a1+a18).n/2
s18=(1+52).18/2
s18=53.18/2
s18=954/2
s18=477