Exponential Growth with Positive and Negative Initial Amount

Exponential growth as a function of time with adjustable rate (0<rate<1) and initial amount (between -5 and 5). f(time) = InitialAmount * (1 + rate)^time

1. What happens at InitialAmount = 0? Why? 2. Compare and contrast the graphs with InitialAmount > 0 and InitialAmount < 0.