Tonya and Leo each bought a cell phone at the same time.
The trade-in values, in dollars, of the cell phones are modeled by the given functions, where x is the number of months that each person
has owned the phone.
Tonya's Phone
Leo's Phone

the trade-in value of
D phone has the greater initial trade-in value.
During the first four months, the trade-in value of Tonya's phone decreases at an average rate
Leo's phone.