can you check my answers?
Find the second difference for the sequence.
7, 6, 7, 10, 15, 22, ….
answer: 1
Find first differences for the sequence in order from a1 to a5. Determine whether or not the series is quadratic or not.
-1, -3, -1, 5, 15
answer: -2, 2, 6, 10; quadratic
Find a quadratic model for the sequence.
-4, -4, -3, -1, 2
answer:y = -4.5x^2 + 21.4x - 21
The 2nd difference is not 1 (7-6).
The 2nd difference is the sequence of differences of the 1st differences. You have
sequence: 7, 6, 7, 10, 15, 22,...
1st diff: -1,1,3,5,7,...
2nd diff: 2,2,2,2,...
2nd ok
3rd. Did you actually try your formula? (Assuming you meant 21.5x)
y(1) = -4
y(2) = -4.5*4 + 21.5*2 - 21 = 4
Try
1/2 (x^2-3x-6)