Question

A car was purchased for $17,000. Each year since the resale value has decreased by 21%. Let T be the number of years since the purchase. Let Y be the resale value of the car, in dollars. Right in exponential function showing the relationship between Y and T.

Answer 1

We know the value is getting smaller, so this is exponential decay

The formula is

y = a ( 1-r) ^x

where a is the initial value

r is the decay rate in decimal form

x is the time interval

y = 17,000 ( 1- .21) ^t

y = 17000 ( .79) ^t