Question

Calcule a soma dos termos da p.a(3,10,17,...150)

Answer 1

an = a1+(n-1).r
150=3+(n-1)7
150-3=7n-7
147+7=7n
154/7=n
22=n

Sn= (a1+an).n/2
S22=(3+150).22/2
S22=153.11
S22=1683