V= 20.8x^2 - 458.3x + 3,500 represents the value of a car from 1964 to 2002. what year did the car have the least value? (x= 0 in 1964)

See the picture for all detail, I have done it by hand.
Few important steps;
-Take the first derivative
-Put it equal to zero
-you get the x value which is equal to 11
-Now for the check that x=11 is the least value or not, take the second derivative
-As, the 2nd derivative is positive so it is the least value

As x=0 in 1964 add 11 to it so at x=11 we get 1975 so in this year car have least value