Respostas

2014-05-19T20:32:04-03:00
R = 9 - 5 = 4 razão da P.A

an = a1 + ( n - 1 ) . r
an = 5 + ( n - 1 ) . 4
an = 5 + 4n - 4
an = 1 + 4n
2014-05-19T20:43:45-03:00
An=a1+(n-1)-r
  9=5+(n-1)-4
  9-5+4n-4
  9-5+4=4n
 8=4n
n=8/4
n=2