What determines whether something is exponential growth or decay is whether the growth factor is greater than or less than 1.
If you multiply by a number greater than 1 your product will always increase. On the other hand if you multiply by less than 1 you will always get a smaller amount.
so
1) growth factor is 1.03 which is >1 so this is exponential growth
2 growth factor is .25 which is <1 so this is exponential decay
3) growth factor is 5.06 which is >1 so this is exponential growth
the last one is neither since if you raise a negative number to an odd power you get a negative number and if you raise it to an even power you get a positive number