The equation is C = 20t^2 + 135t + 3050
You are told the total number of cars sold is 15000.
Replace c with 15,000 and solve for t:
15000 = 20t^2 + 135t + 3050
Subtract 15000 from both sides:
0 = 20t^2 + 135t - 11950
Use the quadratic formula to solve for t.
In the quadratic formula -b +/-√(b^2-4(ac) / 2a
using the equation, a = 20, b = 135 and c = -11950
The formula becomes -135 +/- √(135^2 - 4(20*-11950) / (2*20)
t = 21.3 and -28.1
T has to be a positive number, so t = 21.3,
Now you are told t = 0 is 1998,
so now add 21.3 years to 1998
1998 + 21.3 = 2019.3
So in the year 2019 the number of cars will be 15000
