Which recursive formula describes the arithmetic sequence $5, 11, 17, 23, ...$?

$a_1 = 5$ and $a_n = a_{n-1} + 6$

$a_1 = 6$ and $a_n = a_{n-1} + 5$

$a_1 = 5$ and $a_n = a_{n-1} - 6$

$a_1 = 5$ and $a_n = a_{n-1} + 5$

Which recursive formula correctly represents the sequence $20, 15, 10, 5, ...$?

$a_1 = 20$ and $a_n = a_{n-1} + 5$

$a_1 = 5$ and $a_n = a_{n-1} - 20$

$a_1 = 20$ and $a_n = a_{n-1} - 5$

$a_1 = 20$ and $a_n = a_{n-1} + (-20)$