Write an exponential decay model for each situation. The value of x for each
value of f(x) will lie between two consecutive whole numbers. List the whole
numbers.
4. initial value: 1,000
decay rate: 20%
f(x) = 500
5. initial value: 1,800
decay rate: 7%
f(x) = 400
6. initial value: 1,200
decay rate: 12.5%
f(x) = 450