Question

numa pa a1=-3 r=5 calcule a soma dos 209 primeiros termos dessa pa

Answer 1

an=a1+(n-1).r
an=-3+(209-1).5
an=-3+208.5
an=-3+1040
an=1037
Sn= (a1-an).n/2
Sn= (-3+1037).209/2
Sn= 1034.209/2
Sn= 216103/2
Sn= 108053