f.4 math-- quadratic functions

a_ahal0

2009-10-24 10:33 pm

1. in an experiment , the temperature T 0C of the solution t mins after adding a substance is given by T=120-(2t-8)^2

a.) how long does it take for the temperature of the solution to attain its maximum? find its maximum temperature.

2. if a ball is thrown vertically upwards at a seed of 10m/s, the distance s m of the ball above the ground after t seconds is given by s= -5(t-1)^2+5.

a.) how long does it take for the temperature of the solution to attain its maximum? find its maximum temperate.

回答 (1)

用戶9112

2009-10-24 10:42 pm

✔ 最佳答案

(1) T = 120 - (2t - 8)^2
Since the square term is always positive, the maximum is attained when this term = 0, i.e. 2t - 8 = 0 => t = 4
It takes 4 mins to attain its maximum of 120 degree C
(2) s = -5(t - 1)^2 + 5
Since the square term is always positive, the maximum is attained when this term = 0, i.e. t - 1 = 0 => t = 1
The maximum height is 5m attained at time t = 1s

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