Let a be the first term and d be the common difference.

Given: a₄ = 9

a₆ + a₁₃ = 40

Now, Consider a₄ = 9

⇒ a + (4 - 1)d = 9

⇒ a + 3d = 9 ……….(1)

Consider a₆ + a₁₃ = 40

⇒ a + (6 - 1)d + a + (13 - 1)d = 40

⇒ 2a + 17d = 40 ………..(2)

Subtracting twice of equation (1) from equation (2), we get,

11d = 22

⇒ d = 2

∴ Common difference = d = 2

Now from equation (1),we get

a = 9 - 3d

= 9 - 6

= 3

∴ AP is a, a + d, a + 2d, a + 3d, …

i.e. AP is 3, 5, 7,9, 11…..