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Difference between Matlab and Wolfram Alpha

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Niklas Kurz
Niklas Kurz 2020 年 7 月 31 日
編集済み: Niklas Kurz 2020 年 7 月 31 日
These problems might occure frequently due to the varied syntax. This time it's about:
solve(x^2-8*x+15<=1)
what gives (according to Matlab): pi and 4. That's wrong or not what I ask for. In contrast Wolfram Alpha gives after typing in the same piece of code the correct solution (in my point of view.) Why is that?

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採用された回答

Jesús Zambrano
Jesús Zambrano 2020 年 7 月 31 日
Hi Niklas,
You need to set 'ReturnConditions' to true to return any parameters in the solution and conditions on the solution. Therefore,
S = solve(x^2-(8*x)+15<=1, 'ReturnConditions',true);
S.conditions,
ans =
x <= 2^(1/2) + 4 & 4 - 2^(1/2) <= x
in(y, 'real')
which is the solution interval: 2.5858 <= x <= 5.4142

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その他の回答 (1 件)

Cam Salzberger
Cam Salzberger 2020 年 7 月 31 日
Hey Niklas,
Technically, both pi and 4 are "correct" results, as if you plug them in, they will fulfill the condition. I think what you are looking for is using the solution = solve(___, "ReturnConditions", true) syntax, as suggested by the solving inequalities example in the documentation.
Also, it would generally be helpful to post what you got from Wolfram as well, so we know what you're expecting.
-Cam

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Niklas Kurz
Niklas Kurz 2020 年 7 月 31 日
Thank you, guys
x <= 2^(1/2) + 4 & 4 - 2^(1/2) <= x
is what I'm looking for.

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