Solve the following equations. (Give your answers correct to 2 decimal places.)
2e^(-2x) + 11e^(-x) -21=0
F.4 AMaths
2010-05-06 3:46 am
回答 (1)
2010-05-06 3:54 am
✔ 最佳答案
2e^(-2x) + 11e^(-x) -21=0Let y be e^(-x) :
2y^2 + 11y - 21 = 0
(2y - 3)(y + 7) = 0
y = e^(-x) = 3/2 ,
- x = In (3/2)
x = In (3/2) = 0.41 (2 dec.places)
or
y = e^(-x) = - 7
- x = In (-7) (rejected)
2010-05-05 19:56:40 補充：
Corrections :
x = - In (3/2) = - 0.41 (2 dec.places)
收錄日期: 2021-04-21 22:13:17
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