I graphed the given points and based on my graph.
x y → EXPONENTIAL
-2 21
1 4
0 1
1 0
x y → LINEAR
-2 6
-1 -2
0 2
1 6
x y → QUADRATIC
-2 12
-1 -2
0 -8
1 -6
x y → EXPONENTIAL
-2 16
-1 8
0 4
1 2
LINEAR FUNCTIONS always maintain a constant slope. In the above linear function, the slope is 4.
EXPONENTIAL and QUADRATIC FUNCTIONS have different slope in every point.
Exponential functions can be identified by the immediate increase or decrease in the value of y resulting to a minimal increase or decrease in the value of x.
Quadratic functions can be identified as such due to the similar points it has after having the vertex.