Page 187 - How To Solve Word Problems In Calculus
P. 187
Since the drink’s temperature after 10 minutes is 20 , u(10) = 20.
◦
u(10) = 30 − 25e 10k
20 = 30 − 25e 10k
−10 =−25e 10k
2 10k
= e
5
2
10k = ln
5
1 2
k = ln
10 5
1 ln )t
2
The temperature function is u(t) = 30 − e ( 10 5 . After
20 minutes the temperature will be
u(20) = 30 − 25e 2ln 2 5
= 30 − 25(e ln 2 5 ) 2
2
2
= 30 − 25
5
4
= 30 − 25
25
= 26 degrees
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