I can't figure out how to find the base of the exponential functions...really ticking me off lol. I'd appreciate any help. I have two different problems

Problem 1:

Determine growth or decay factor

x |-2 | -1 | 0 | 1 | 2 | 3 | 4

___________________________

y|6.25|2.5 | 1 | .4 | .16|.064| .0256

the decimals really screw it up, and I've tried many numbers...is there any kind of formula to figure this out? our teacher just told us that we might have to do some "guess work"

Problem 2:

Assume that y is an exponential function of x

If the growth factor is 1.08, then complete the following table

x 0 | 1 | 2 | 3

_____________________

y 23.1|

They gave me the first Y point... I can't figure out any of the others...I'm pretty bad at math...if anybody knows a formula I'd greatly appreciate it.