Respostas

2013-12-02T11:21:10-02:00
A1 = x
r = 500
n = 15
Sn = 675000

an = a1+(n-1).r
an = x+(15-1).15
an = x+14.15
an = x + 210

Sn = (a1+an).n/2
675000 = (x+x+210).15/2
675000 = (2x+210).15/2
2 x 675000 = 15.(2x+210)
2x+210 = (2 x 675000)/15
2x+210 = 1350000/15
2x+210 = 90000
2x = 90000 - 210
2x = 89790
x = 89790/2
x = 44895
an = x+210
an = 44895+210
an = 45105 (último dia)