one equation with one unknown variable
显示 更早的评论
Hello,
I want to solve equation with one unknown variable (x).
Matlab code: Editor: function y = f(x)
y=(18/5)*((1-x)^(-1/6))-(162/29)*((1-x)^(-1/9));
Command window: x=fzero(@f,[0,1])
(x should be between 0 and 1)
And the error is: ??? Error using ==> fzero at 283 The function values at the interval endpoints must differ in sign.
What should I do to solve that equation correctly?
And help will be appreciated.
采纳的回答
Konstantinos Sofos
2015-3-15
编辑：Konstantinos Sofos
2015-3-15
Hi,
fzero checks that fun(x0(1)) and fun(x0(2)) have opposite signs, and errors if they do not. In you example the upper bound gives NaN
>> y=@(x)(18/5)*((1-x)^(-1/6))-(162/29)*((1-x)^(-1/9))
y =
@(x)(18/5)*((1-x)^(-1/6))-(162/29)*((1-x)^(-1/9))
>> y(0)
ans =
-1.9862
>> y(1)
ans =
NaN
Regards
更多回答（1 个）
Roger Stafford
2015-3-15
I would recommend that you alter the interval:
x=fzero(@f,[0,.999999]);
There is an easier way of solving it. Substitute t = (1-x)^(-1/18) and get an equation in t, which can be easily solved. From that you can get back to a solution for x.
4 个评论
John D'Errico
2015-3-15
As Roger points out, the transformation is the correct way to do it - a slam dunk solution.
Lojzika
2015-3-15
John D'Errico
2015-3-15
I am confused as to why you would accept the other answer as this is so clearly the correct one. Oh well, Roger's answer got my vote.
Konstantinos Sofos
2015-3-15
@John D'Errico could you explain us also why my answer is not valid or the correct one? Do we have any competition here or shall we try to provide our view? I am sorry for your comment...
类别
在 帮助中心 和 File Exchange 中查找有关 Computational Geometry 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
