Question

calcule a soma dos termos da pa infinita (25,39,53.. 375)
ME AJUDAAA

Answer 1

a1 = 25
a2 = 39
r = a2 - a1
r = 39 - 25
r = 14

an = a1+(n-1).r
375= 25+(n-1).14
375-25= 14n - 14
350 = 14n -14
350+14 = 14n
364 = 14n
364/14 = n
N =26

SN = (a1 + an).n / 2
S26 = (25 + 375).26/2
S26 = 400.26/2
S26 = 200.26
S26 = 5200