1, 4, 8, 13, 19, 26

Find sequence formula using the quadratic way.

1/2 n^2 + 3/2 n - 1.

Step-by-step explanation:

1 4 8 13 19 26

Differences 3 4 5 6 7

2nd Diff: 1 1 1 1

This means that a in the formula a^2n + bn + c = 1/2 (as 2a = 1).

Now The first difference is 3 and we plug this into the formula:

3a - b = first difference

3 (1/2) + b = 3

b = 3 - 3/2 = 3/2.

So we have the formula 1/2 n^2 + 3/2 n + c

So using the first term 1 : 1/2 (1) ^2 + 3/2 + c = 1

c = 1 - 3/2 - 1/2 = 1 - 2 = - 1.

Formula is therefore 1/2n^2 + 3/2 n - 1.

Step-by-step explanation:

1 (8) ^2-1

its the first variable then the the third one and u raise it by what the number is and u subtract by one