Question

The sequence 4,9,x,37......is a quadratic sequence calculate x

Answer 1

4, 9, x, 37

first difference:

5, x-9, 37-x

2nd difference

x-14, 37-x - (x-9)

x-14, 46-2x

To be a quadratic sequence, the 2nd differences must all be the same, so

x-14 = 46-2x

3x = 60

x = 20

so our terms are 4, 9, 20, 37

Explanation: