DESPARATE WILL GIVE 100 POINTS FOR THIS Which table represents a nonlinear function?

x y
−2 −1
0 1
2 3
5 6

x y
−7 −3
−5 0
0 3
4 1

x y
−5 7
−2 6
1 5
7 3

x y
−3 3
0 0
6 −6
10 −10

The fence around a quadrilateral-shaped pasture is 3a^2+15a+9 long. three sides of the fence have the following lengths: 5a, 10a-2, a^2-7. what is the length of the fourth side of the fence?