Question

Find the nth term of this quadratic sequence:
4, 7, 12, 19, 28

Answer 1

n^2+3

Explanation:

Step 1:

Work out the first differences and that is 3, 5, 7, 9.

Step 2:

Find the second difference and that is 2.

Step 3:

Since half of 2 is 1, then the first term is n^2.

Step 4:

Subtracting n^2 from the sequence gives 3.

So the answer is n^2 + 3.