well, just look at the differences:
1st differences: -2 2 6 10
2nd differences: 4 4 4
Looks quadratic to me.
Find first differences for the sequence in order from a_1 to a_5. Determine whether or not the series is quadratic or not.(I used _ as a sign for a subscript)
-1, -3, -1, 5, 15
A. 2, 2, 6, 10; not quadratic
B. 2, 2, 6, 10; quadratic
C. -2, 2, 6, 10; not quadratic
D. -2, 2, 6, 10; quadratic
1 answer
1 answer