1. ## [SOLVED] formula needed

hey, before i can complete the invstigation i need to do, i need to work out a formula. the investigation ive been working on is what affects the price of second hand cars. ive looked at three factors, which are the mileage, age and whether the car is european or not. from these i need to conduct a formula to work out what the price depreciation of a new car would be in x amount of years.
To work out the percentage depreciation of the price from the age of the car i have the equation y = 33.173Ln(x) + 14.444 where x = the number of years. from this i need to devise the formula.

pls can anyone give me somewhere to start? all i need is a lead and i should be able to crack it. if anyone has any ideas pls can you let me know?
help would be greatly apprechiated.

thank you for taking the time to read this, charlie.

2. If mileage is a determinant factor in your equation, then you should give it a limiting age like 150,000 or 200,000 miles. European resells are higher than American or Asian, so you could use a variable that takes an input of zero or one.