Step 1 — initial value: At t = 0 the car is worth $42,000, so a = 42000.
Step 2 — annual decay factor: A 17% decrease each year means the car keeps 100% - 17% = 83% of its value each year. As a decimal, the yearly factor is b = 0.83.
Step 3 — exponential model: The value t years after purchase is the initial value multiplied by the decay factor raised to the t power.
Final answer: V(t) = 42000(0.83)^t