The temperature, T (in ºF), of a car's radiator during the first 4 minutes (t 4) is given by T = 6.2t2 +12t +32. How long does it take the temperature to reach 120 ºF after the car has begun operating?
Assuming radiator reaches 120° between 0 and 4 minutes.
Trying to solve:
120 = 6.2t² + 12t +32
or
6.2t² + 12t - 88 = 0
Use quadratic formula to get
t=-4.8 or t=2.92 sec.
Reject t=-4.8 because it is not within interval [0,4].