pp2-161

Kath1985 · 发表于 2010-4-25 00:01:15

161.16989-!-item-!-187;#058&011313

The temperature of a certain cup of coffee 10 minutes after it was poured was 120 degrees Fahrenheit.If the temperature F of the coffee t minutes after it was poured can be determined by the formula F = 120[2^(-at)] + 60, where F is in degrees Fahrenheit and a is a constant, then the temperature of the coffee 30 minutes after it was poured was how many degrees Fahrenheit?

(A) 65

(B) 75

(C) 80

(D) 85

(E) 90

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【答案】B
按PP說的先將10帶入方程式t得位置求出a 再將30帶入方程式求出解
但是120*2^15+60 怎麼樣也不可能等於75呀哪裡錯了呢

草稿纸 · 发表于 2010-4-25 00:34:46

a=0.1

pp2-161

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