Growth Factor

to get the growth factor (or the base) from the table of values

Scale_differences

x	y	$\nabla y_1$
-2	$-\frac{1}{9}$
-1	$-\frac{1}{3}$	3
0	1	3
1	3	3
2	9	3
If you find the scale from one value of y to the other, and they are all the same, you will find the base.