Posted by Cassie on .
Which kind of function best models the data in the table? Use differences or ratios.
x y
0 1.7
1 6.8
2 27.2
3 108.8
4 435.2
A.linear
B.quadratic
C.exponential
D.none of the above
I think it is C...?

Algebra 
Damon,
first difference table
6.8  1.7 = 5.1
27.2  6.8 = 20.4
108.8  27.2 = 81.6
435.2  108.8 = 326.4
so not linear
second differences
20.4  5.1 = 15.3
81.6  20.4 = 61.2
326.4  81.6 = 244.8
so not quadratic
try ratios
6.8/1.7 = 4
27.2/6.8 = 4
ah hah ! constant ratio of 4 
Algebra 
Reiny,
looks like
y = 1.7(4)^x 
Algebra 
Damon,
sorry about repeat
yes, 1.7 * 4^x