Question

dada a Pa (4 9 14 ... 99 ) calcule a soma de seus termos

Answer 1

Sn = (a1+an).n/2
Sn = (4+99).n/2
a1 = 9
an = 99
r = 5
an = a1+(n-1).r
99 = 4+(n-1).5
99-4 = 5n-5
95+5 = 5n
5n = 90
n = 90/5
n = 18
Sn = (4+99).18/2
Sn = 103 x 9
Sn = 927