Question

Calcule a soma dos 30 primeiros termos da PA (2,4,6,8…)

Answer 1

a1= 2      r = a₂-a₁= 4-2=2

an= (a1+(n-1)r

a₃₀= 2+(30-1)2
a₃₀= 2+58= 60

Sn= (a1+an)n/2
S₃₀= (2+60) 30/2
S₃₀= 63x30/2 = 930