Questions on the analytic and numeric equation solving functions of Mathematica (Solve, Reduce, NSolve, FindRoot, DSolve, RSolve, etc.).

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0
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0answers
135 views

Can't Solve a system of differential equations, Solve takes too long

My question is probably not really interesting but I really need help on this because I won't have access to a more powerful computer. So my model contains 7 equations : ...
1
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2answers
2k views

Solve within a range?

Is it possible to solve an equation in which some some of the parameters have defined ranges? Example: ...
1
vote
2answers
853 views

Projection of curve 3D (x,y,z) on the x-y plane

I have a following systeme : \begin{equation} \left\{ \begin{array}{rcr} (\beta+\frac{1}{2}\delta^{2})\nu_{1}(u)-\delta\nu_{2}(u)+\nu_{3}(u)& = &0\\ (\beta+\frac{1}{2}\delta^{2})\...
0
votes
1answer
100 views

RSolve works slow and does not give an analytical solution for solving high order linear difference equations

RSolve@@{{a[n]-a[n-10]==101}~Join~Table[a[i+1]==101+10i,{i,0,9}],a[n],n} I want to get the exact form of general formulas, but ...
0
votes
2answers
490 views

Symmetric function of the roots of a polynomial

First, I'm a beginner. I can compute the sum of roots with the follwing: Roots[x^7 + 5 x^6 + x^5 + x + 1 == 0, x] Plus @@ (x /. {ToRules[%]}) // Simplify Of ...
3
votes
3answers
244 views

Can Mathematica solve $x^{b^2} + ax^b -1 = 0$ for $x$ with $a>0$, $b>1$?

I have a problem that I can't seem to solve neither analytically nor with Mathematica. Namely, I have the expression $$x^{b^2} + ax^b - 1= 0,$$ which I want to solve for $x$ with $a>0$, $b>1$. ...
0
votes
1answer
423 views

Solve function doesn't work

I have the following system of equations that I need to solve: ...
0
votes
1answer
194 views

Nonlinear system of equations

I have been working to find an equilibrium solution for a Hamiltonian dynamical system. I have reduced the problem to the simultaneous solution of 3 equations: ...
0
votes
1answer
198 views
0
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1answer
122 views

NSolve cannot find the solution [closed]

I have some data which looks like: ...
0
votes
1answer
61 views

NSolve stalls when given an equation containing Log

Why does NSolve not work for this type of equation? ...
8
votes
2answers
264 views

What are the Method options Solve command accepts?

What are the Method options Solve command accepts? Solve has the Method option, however documentation contains no methods that it accepts...
3
votes
0answers
172 views

Solving Thue equations

A Thue equation is a 2-variable homogeneous integer polynomial of degree at least 3. It's well-known that such equations have only finitely many solutions over the integers. I'm trying to solve some ...
2
votes
1answer
99 views

Strange behavior using variable in Exists

I came across a behavior that doesn't make sense to me when I tried to use Exists in Reduce. If I run commands: ...
3
votes
3answers
531 views

Is there a way to specify custom domains?

I want to solve for all solutions to the system of equations $a_1 a_2 a_3 b_4 + a_1 a_2 b_3 + a_1 b_2 + b_1 = 0$ and $a_1 a_2 a_3 a_4 = 1$ where the $a_i$'s and $b_i$'s take on values from $\{-1,1\}$. ...
2
votes
1answer
115 views

Problem with SquareWave in NDSolve

I would like to have a triangulare signal drive a ODE system, using SquareWave[]. Something seems to go wrong though during integration. Uext'[t] and ...
4
votes
1answer
616 views

What algorithms does NSolve use?

I've been using NSolve to find roots and now I've been wondering what underlying algorithm Mathematica uses. It's probabaly similiar to ...
-2
votes
1answer
215 views

How to solve a non-linear equation?

I am trying to solve the following non-linear equation: $\frac{i e^{-x^2} \sqrt{\pi } x}{K^2}+\left(-0.131251-0.0379031 x^2-0.0151154 x^4-0.0100462 x^6+0.5 \left(0.00273859 +0.0400003 K^2\right) x^8+(...
0
votes
1answer
830 views

Solving a large system of non-linear equations

I am new to Mathematica, and I am currently trying to use it to solve a large symbolic system of non-linear equations. I began the code below about 30 hrs ago, and the Mathematica Kernal has been ...
3
votes
0answers
321 views

Function with a sharp resonance which Mathematica fails to integrate. Why?

I'm a new user of Mathematica and I'm trying to use it to calculate the collisional cross-section as a function of energy for a given potential and decay rate. I know that the resulting function ...
0
votes
0answers
43 views

Verify “Type” of solution [duplicate]

I've written some Mathematica functions which allow the user to verify if a mathematical function has certain properties. What I'm basically doing is generating "random" functions in respect of ...
0
votes
1answer
269 views

Notebook keeps running when Solve for variable

This might be a simple question for the most of you, but I am very new to mathematica so please bear with me. I'll refer to the code below: ...
4
votes
2answers
2k views

What is the efficient way to code Successive Over-relaxation (SOR) method in Mathematica?

I have written a SOR method (SOR is this method) code using C-style procedural loops. However, I think there might be (much) better ways to achieve the same end in Mma avoiding these loops. So my ...
1
vote
1answer
359 views

How can I find a root of my transcendental equation near a certain point?

What function could I use to solve this equation for x: E^(-x^2) = 1 - Cos[x] I tried Solve, ...
6
votes
2answers
213 views

Solve a system of M equations without specifying M [on hold]

I am trying to write my game-theoretic model in Wolfram Language. There is only one remaining step and I am not sure if it is within reach of Wolfram Language (or Mathematica). I describe a simplified ...
1
vote
0answers
27 views

Minimizing roots of a transcendental equations [duplicate]

I'm trying to use the solution of FindRoot with parameters for further calculations. Annoyingly enough it always gives me trouble with replacing the parameters. As an example I'm attaching a simple ...
0
votes
1answer
144 views

Two questions on strategies for quantifier elimination

With the help of people here I was able to solve several cases similar to IC3 but this case - unlike the other cases - does not return an answer. I will try to run it for a day with 8 processors but ...
11
votes
3answers
950 views

Finding “Maxima” and “Minima” on a B-Spline

I need to find the "Maxima" and "Minima" on a B-Spline or more correct the points where the 2nd components of the derivate equal zero. For example: ...
1
vote
0answers
38 views

Correct use of Mathlink's MLGetRealList

I am attempting to use Mathlink from C. I have managed to return single values from mathlink to my c program, but I am having trouble with lists. Consider the Mathematica operation: ...
2
votes
0answers
1k views

FindRoot in range

I am trying to find all roots in a range, using y /. FindRoot[Sin[y] == 0, {y, #}] & /@ Range[7] which gives ...
4
votes
3answers
515 views

Finding parameters making real part of eigenvalues vanish

I have the following $\;3\times3$ matrix: $\left( \begin{array}{ccc} 0.04 -0.4 b & 0 & 0.04 -0.4 b \\ 0 & -0.08-1.2 b & -0.06-0.9 b \\ 1.04 -0.4 b & 2.08 -0.8 b & 0 \end{...
0
votes
1answer
67 views

Help with Reduce, quadratic system of inequalities

I'm trying to obtain an equivalent system of inequalities to the one below but without the variables x and z. Somehow Reduce just repeats the command. ...
0
votes
4answers
163 views

RSolve fails on a two-equation non-linear system

I have a system of just two recurrence equations, I need to solve them and so I use RSolve: ...
1
vote
1answer
555 views

Why my differential equations become True? [duplicate]

I've been trying to solve a system of nonlinear differential equation, but the conditions are a bit weird. Two of the differentials equate to the same equation, but have different boundary ...
1
vote
1answer
313 views

Get Cos[2 x] in “Solve”

My goal is to get an analytical solution of x ( $\lambda$ in the problem), when $\epsilon$ (f[x] in the problem) is maximum (use inverse form). I found that if I can use trigonometric identity to ...
0
votes
1answer
111 views

Equation in implicit form

This is simple example: v = {1.48622576, 1.53444276, 1.42299438} v/(v + 1) Out[1]:= {0.597784, 0.605436, 0.587288} In the above case expression v/(v + 1) is ...
0
votes
1answer
712 views

Solving a system of equations where two variables can only be one of several discrete values

I want to solve a three-equation system, but I need to constrain two of the variables so that they can only take one of several discrete values that I would specify (this is a circuit design problem ...
3
votes
0answers
155 views

Solving huge equations

I have this expression: $d=-\frac{\sqrt{\frac{780 (f+130) \left(5 d^2 (13 c+f+130)-5 d (c (f+1300)-325 (f+160))+125 \left(2 (2 c+725) f+5 f^2+104000\right)+13 d^3\right) \left(5 d^2 (52 c+17 f+...
-1
votes
1answer
243 views

Mathematica Compute Time Is Extremely Long (Integrate simple function with parameter scan)

I was wondering if you can help. I have a set of equations I need to solve for a list of parameters; entering each parameter value and solving anew each time is simply not economical. I found a way ...
2
votes
0answers
57 views

How can I select two lists from a list of lists so that I receive the system of equations has only rational solutions?

I want to make a sytem of equations has the form $$\begin{cases} a_1x^2+b_1y^2 + c_1xy+d_1x + e_1y+3=0,\\ a_2x^2+b_2y^2 + c_2xy+d_2x + e_2y+3=0. \end{cases}$$ so that the given system of equations has ...
1
vote
1answer
78 views

Solve never terminates with simultaneous equation set

I have the following set of simultaneous equations that I want to solve symbolically. The two unknowns are $a$ and $d$. $a=\frac{c*(d/10)}{1 + (f/130) + (d/50)} - \frac{a}{1 + (a/100) + (d/100) + (f/...
1
vote
1answer
439 views

Marking the points of x-intercept on a plot

OK, I have a nice plot of some oscillating motion. I can read some stuff off the graph, but I thought it would be cool to show a dot where the curve hits the x-axis and a little label showing the ...
1
vote
1answer
185 views

How do assign an interval of values to a variable in order to use them in a function?

From my code (below) I have K1 and K2 set to zero in order to test this numerical method. However, K1 is on an interval from 0 to 32, and K2 is on an interval from 0 to 8. I would like to know if ...
1
vote
1answer
115 views

A simple expression which Mathematica will not simplify

Sorry for the vague title, but I wasn't sure how to phrase this. I was using Mathematica to solve a fairly simple algebraic equation, but when I tried to substitute the solution into the original ...
5
votes
1answer
539 views

Solving a nonlinear, second order d.e. in Mathematica

I am trying to solve the following differential equation $$ s''(x) = \frac{8}{9}s(x) -2s^2(x) + s^3(x), $$ with boundary conditions $s(-30) = 4/3 $ and $s(30)=0$, in Mathematica by using the following ...
0
votes
3answers
639 views

How to solve correctly inside a DO loop and then plot

Here is the corresponding code First the equations setup ...
1
vote
0answers
24 views

Solving a pair of recurrence relations [duplicate]

Why does this RSolve[{y[t] == a*y[t - 1]}, {y[t]}, t] work, while this ...
11
votes
3answers
701 views

1D quasicrystal: points on a line nearest to points on a lattice

I have a simple lattice / line manipulation: ...
0
votes
1answer
287 views

Solving a system of two equations of third degree

I am trying to solve the following system of two equations for x and y. The solutions for x and y have to be positive and the parameters s and c are positive (to have a coherent interpretation of my ...