Question

Calcule a soma dos 50 primeiros termos da P.A (2,6...)

Answer 1

an=a1+(n-1)r
an= 2 +(50-1).4
an= 2 + 49.4
an = 2 + 196
an= 198

soma: 
sn=(a1+an)n/2
Sn= (2+198).50 / 2
Sn = 200.50/2
Sn= 10000/2
Sn= 5000