Question

(3,9,15,21...)A43=? Quero a respostas

Answer 1

A43 = 3 + (43 - 1)6
A43 = 3 + 252
A43 = 255

Answer 2

$r = a_2 - a_1 \\ r = 9 - 3 \\ r = 6 \\ \\ a_n = a_1 + (n - 1) * r \\ a_{43} = 3 + (43 - 1) * 6 \\ a_{43} = 3 + 42 * 6 \\ a_{43} = 3 + 252 \\ a_{43} = 255$