It's pretty easy to go through the choices and none has a[2]=-36 and a[5]=2304. Something's probably wrong with the way the question is typed, but I will answer what's written.
[tex]a_n = a + (n-1) d[/tex]
[tex]a_2 = -36 = a + d[/tex]
[tex]a_5 = 2304 = a + 4d[/tex]
Subtracting,
[tex]2340 = 3d[/tex]
[tex]d = 2340/3 = 780[/tex]
[tex]a = -36 - d = -36 - 780 = -816[/tex]
Answer: a[n] = -816 + 780(n-1) which is none of the above
Check:
[tex]a_2 = -816 + 780= -36 \quad\checkmark[/tex]
[tex]a_5 = -816 + 780(4) = 2304 \quad\checkmark[/tex]
