In the year 2005, the average cost of a car could be modeled by the equation C= -15x2 + 20x - 3 where x is the number of years since 2005. By the year 2010 the average cost had changed, and the equation could be modeled by C= -10x2 + 30x - 2. Find the difference in average cost equation for cars between 2005 and 2010.

Please help as soon as possible!

I got this by plugging in the number 5 for x since it said that x equals the amount of years it has been since 2005. I got 5 since it is talking about the relationship between 2005 and 2010 (2010-2005=5). Therefore you would get the equation -15 x 2 + 20 (5) -3 = -10 x 2 + 30 (5) -3. First you would do the left side of the equation, start with multiplication from left to right and then addition and subtraction from left to right. You would then get 67 = -20 + 30 (5) -3. You would again start with the multiplication and the addition and subtraction from left to right. You would end up with 67 equals 127. You would subtract 167 from 127 to get 60 dollars which is the difference from the years. I hope this helps and is right.