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### Finding common roots of two multivariate equations

I am trying to find points of a surface whose normal is parallel with the 3 dimensional axes (i.e. local maxima, minima and saddle points in x, y and z dimensions). The function of the surface is ...
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### Fastest method forfinding a solution to x*log(x)

more specifically, $C x \log_2(x)- K = 0$, where $C$ and $K$ are constants ($\log_2$ means log base 2). I was solving a topcoder problem, SortEstimate, which requires us to solve the aforementioned ...
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### Solution of quartic equation

Is there a open C-implementation for the solution of quartic equations: $$ax⁴+bx³+cx²+dx+e=0$$ I am thinking of an implementation of Ferrari's solution. On Wikipedia I read that the solution is ...
I appologize in advance if this question is silly. I need to compute the root of $$u -f(u) =0$$ Where $u$ is a real vector and $f(u)$ is a real-vector valued function. ...