Answer:
X represents the time, in this function.
Step-by-step explanation:
1) Since in Alexander's savings account the Interest is also compounded, then this function is properly written this way:


Replacing A for f(x) this function tells us that for a given period (x). This savings account with a principal of $500, and 20% interest compounded annually will provide us how much he earns.
Further explanations
3) In case you want to calculate the accrues (accumulated) interest of this saving account, after having found the time, you have to know whether it is daily weekly or monthly accrued, etc.
For example:
Daily interest accrued (accumulated)= 20% (0.2) : 360 days =

Supposing 31 days after the investment, Alexander will have from his $500 this interest payable:
