## Algebra 2 (1st Edition)

$a_n=n \times 9n= 9n^2$
Given : $9,36, 81, 144,225$ Re-arrange as: $9(1), 18(2), 27(3), 36(4), 45(5)$ The above sequence yields the relation: $a_n=n \times 9n= 9n^2$