Answer:
[tex] a_n = 2n^2 + n + 1 [/tex]
Step-by-step explanation:
4, 11, 22, 37, 56
11 - 4 = 7
22 - 11 = 11
37 - 22 = 15
56 - 37 = 19
After the first difference, 11 - 4 = 7, each difference is 4 more than the previous difference.
Difference of differences:
11 - 7 = 4
15 - 11 = 4
19 - 15 = 4
Since we need the difference of differences to find a constant, this must be a second degree function.
[tex] a_1 = 4 = 2^2 + 1(0)[/tex]
[tex] a_2 = 11 = 3^2 + 2 = 3^2 + 2(1) [/tex]
[tex] a_3 = 22 = 4^2 + 6 = 4^2 + 3(2) [/tex]
[tex] a_4 = 37 = 5^2 + 12 = 5^2 + 4(3) [/tex]
[tex]a_5 = 56 = 6^2 + 20 = 6^2 + 5(4)[/tex]
[tex] a_n = (n + 1)^2 + (n)(n - 1) [/tex]
[tex] a_n = (n + 1)^2 + (n)(n - 1) [/tex]
[tex] a_n = n^2 + 2n + 1 + n^2 - n [/tex]
[tex] a_n = 2n^2 + n + 1 [/tex]