Question

Determine o numero de termos da P.A. (5,9,13...,37)?

Answer 1

(5, 9, 13, ..., 37)
a₁ = 5
r = 9 - 5 ----- r = 4
37 = 5 + (n - 1) . 4 ------37 - 5 = (n - 1) . 4 ------n - 1 = 32/4
n - 1 = 8 ---- n = 8 + 1 ---- n = 9

Answer 2

$a_n=37 \\ a_1=5 \\ r=9-5=4 \\ n=? \\ \\ termo~~geral \\ \\ a_n=a_1+(n-1)r \\ \\ 37=5+(n-1)(4) \\ 37=5+4n-4 \\ 37=1+4n \\ 37-1=4n \\ 36=4n \\ n=36\div4 \\ \\ n=9\mapsto n\'umero~~de~~termos$