Final answer:
The independent variable is the number of days late and the dependent variable is the final cost to rent the DVD. The function notation for this situation is f(d) = 3.99 + 0.99d.
Step-by-step explanation:
The independent variable in the scenario "To rent a DVD, a customer must pay $3.99 plus $0.99 for every day that it is late." is the number of days the DVD is late. This is because the number of days is the variable that is being changed or controlled in this situation. The dependent variable is the final cost to rent the DVD. This is dependent on how many days the DVD is returned late.
In function notation, the equation representing this situation would be: f(d) = 3.99 + 0.99d, where f(d) represents the final cost and d represents the number of days late. The y-intercept in this linear equation is $3.99, which is the initial cost to rent the DVD, and the slope is $0.99, which represents the additional cost per day for a late return.