the number of N of digits after the decimal point of the number 22/5 that Alex recites correctly after t days of practice is given by
N=1000-985e^(-0.08t)
if the number of digits that Alex recites correctly after x days of practice is 15 more than tat in the previous day, find the value of x
(x=21)
please show the steps
數學 exponential
2010-01-14 11:24 pm
回答 (1)
2010-01-15 12:15 am
✔ 最佳答案
1000-985e^(-0.08x) - [1000-985e^(-0.08(x-1))] = 15985e^(-0.08(x-1)) - 985e^(-0.08x) = 15
e^(-0.08(x-1)) - e^(-0.08x) = 3/197
e^(-0.08x + 0.08) - e^(-0.08x) = 3/197
[e^(-0.08x)] * (e^0.08) - e^(-0.08x) = 3/197
[e^(-0.08x)] (e^0.08 - 1) = 3/197
e^(-0.08x) = (3/197) / (e^0.08 - 1)
e^(-0.08x) = 0.182842628
- 0.08x = In 0.182842628
- 0.08x = - 1.699129447
x = 21.239......
x = 21(nearest days)
收錄日期: 2021-04-21 22:07:29
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20100114000051KK00728