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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1answer
30 views

Undershoot/Overshoot Method for this differential equation?

I have tried to solve this equation for some weeks and I am not capable. I have read in articles that it is easy with an undershoot/overshoot method, but I don't know how to do it. ...
1
vote
0answers
50 views

Solve equations with Monte Carlo

I am dealing with a complicated problem. I will use a simple problem to explain it. I have two variables x and y, and two equations: x+y=A 2x+y=B The value of A and B is determined by measurement, ...
0
votes
1answer
75 views

Solving Boolean equations

I would like to have Mathematica solve this system of equations but I have no clue how I can best integrate those "if" lines. Can you give me a hint or some lines of code?
0
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1answer
42 views

Solving and Plotting Infinite sums over solutions to transcendental equation involving Bessel functions

I am trying to use Mathematica to plot the following equation $E(q,\Delta)$ vs $qa$, for set values of $ D \Delta/a^2$ and $\bar\rho a/D$. I have looked at other stackexchange posts which deal with ...
0
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1answer
41 views

Stopping NDSolve when encountering stiffness

I am solving a differential equation for different initial conditions using ParametricNDSolveValue. I need to look at the value of the solution at some later point, ...
0
votes
1answer
25 views

Probems using 2 For and a AppendTo to cycle through my Equation to solve some matrixes

I am trying to solve a few problems here. I have an equation with multiple variables that I am trying to solve in For loop method. I will attach the file below. In addition I am trying to get it to ...
0
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0answers
16 views

build absolute value equations know solution [migrated]

We have absolute value equations with unknown coefficients: |x + a| = b and we know solutions: x = 11 and x = 5 We need ...
2
votes
1answer
46 views

Finding an Integer, Unimodular Matrix that connects two given matrices

I have two symmetric, integer matrices, $K$ and $K_2$ which have the same determinant and the same signature (number of positive - number of negative eigenvalues). I want to find an integer valued ...
0
votes
1answer
47 views

Solution of Coupled second-order ODEs and plot the diagram

We have two second-order Coupled differential equations as the followings: $$\left\{\begin{array}{lr} \displaystyle \frac{{{d^2}{y_1}}}{{d{x^2}}} = \{ \frac{{\sqrt {\frac{{1 - {\varepsilon ...
-1
votes
1answer
101 views

Solve an equation in several variables

I'm new to Mathematica, so my question may be quite trivial, but I need help. Let $F(x,y,a,b,c,d):\mathbb{R}^6\rightarrow \mathbb{R}$ be a function in 6 variables. I need to find conditions for $x$ ...
0
votes
1answer
34 views

Solving a polynomial where variables are constrained to take only some values

I want to find out which combinations of 1's and 0's would make this kind of equation be null: ...
0
votes
2answers
52 views

How to solve polynomial equation using Mathematica? [on hold]

Solve for $x$ the following equation. $$(ax+b)(cx+d)=(cx+f)(ax+g)$$ Where $a,\,b,\,c,\,d,\,f,\,g$ are constants.
1
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2answers
73 views

FindRoot with Grad

I want to find a numeric solution using Grad. With Solve, I get ...
1
vote
1answer
41 views

REAL Roots of a 2 variable Polynomial

I am looking to plot the real zeros of polynomials of two variables in Mathematica, but I have encountered an issue. To accomplish this task I have been using ContourPlot to plot the polynonial ...
0
votes
0answers
75 views
0
votes
1answer
52 views

Solving for Polynomial roots

This simple Solve gives the roots of a quadratic: Solve[a x^2 + b x + c == 0, x] However, if I factor the polynomial in terms ...
0
votes
0answers
54 views

Equation cannot be solved with the methods available to Solve [duplicate]

I am a beginner to Mathematica. I am trying to get the solution of such equation as: Solve[-b*M + L*R - a*M*Log10[L*c + (L*d*(1 - M)*S)/R] == 0, R] Constants are ...
0
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0answers
35 views

Create a loop for assignment of Solve output [duplicate]

Is there a way to automatically assign the output of solve to a number of symbols? For example, assume that I have the solve statement as follows: ...
0
votes
0answers
52 views

The ` in Solve results [duplicate]

I assign the result of a Solve to the variable eq8. Then I attempt to use this result in the definition of a function as follows: ...
2
votes
2answers
46 views

Difficulty finding roots of an interpolation function from NDSolve

I have been trying to find the point at which one of the solutions of a system of two ODEs crosses zero. I used the method suggested in this answer to a previous question, which seemed to be the most ...
0
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0answers
17 views

Schmidt decomposition problem [migrated]

I'm having a problem in implementing the following problem: I have a quantum state so defined: $\left| \Psi\right>=\int ...
4
votes
1answer
80 views

Trying to create an interactive plot (newbie here)

I'm new at Mathematica so please bear with me. I am trying to create an interactive plot that will end up looking like this: I want to input values for certain variables and then plot a curve. This ...
1
vote
1answer
40 views

How to define a Reduce function in order to define two parameters afterwards

I'm trying to evaluate numerically an equilibrium for a system of ODEs: dA = c A + b B - a A dB = d B + a A - b B So I define a list of known parameters: ...
3
votes
1answer
61 views

Solve with Reals gives different answer

I'm very new to Mathematica (started using ver 10.4) and I was just verifying my calculations. I have the following equation: ...
0
votes
0answers
3 views

Find all solutions to the equation over field Z_16 [migrated]

So for the first part of the question, I have to find the solutions to: $\ x^2+4x+3=0$ over $\ Z_(16)$ I have found these to be X=5,7,13 and 15, just by using standard method to solve a quadratic ...
-1
votes
1answer
153 views

Can Mathematica solve this integral numerically?

I need to evaluate numerically the following ...
1
vote
1answer
54 views

Testing equivalence of analytical expressions like $x^2 -x == x(x-1)$

On occasion I have two expressions that I may be equal but simplified differently, and I want to check if they are actually equivalent. Using the equation in the title, $x^2 -x == x(x-1)$, sometimes ...
0
votes
2answers
39 views

Solving several inequalities in Mathematica

I am a very beginner of Mathematica and the following will probably be a very stupid question. I have a bunch of inequalities in 6 unknowns and I want to find the set of values satisfying them. Can I ...
0
votes
2answers
71 views

FindInstance is very slow on an apparently simple problem

I wish to use FindInstance to find a set of solutions of this problem: ...
0
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0answers
44 views

How to make sure that Mathematica doesn't hog memory for intermediate steps while using functions like FindRoot? [closed]

I am using Mathematica 10.4. I am trying to solve a set of around 10000 non-linear algebraic equations that I have computed upon discretization of a set of coupled non-linear differential equations. ...
0
votes
1answer
49 views

Errors only when code is iterated

Hello I'm trying to have two for loops sweep two parameters and for each 2-tuple of those parameters I want to solve a differential equation. To do this I have the following code: ...
6
votes
2answers
249 views

Find a condition that b must satisfy so that Ax=b has solution

I'm new to Mathematica, so I'm sorry if this is really simple. I am trying to find the condition that vector b must satisfy so that Ax=b has solution. I would like to learn a general method, but I'll ...
5
votes
4answers
171 views

Solving Recurrence Equation $a_{n+1}=a_n(1-a_n)$

How to solve following recurrence equation $$a_0=2$$ $$a_{n+1}=a_n(1-a_n)$$ I tried: ...
0
votes
0answers
27 views

Finding results using qualifiers?

I have set of recursive function definitions and assumptions $\forall n.t1(n+1)=t1(n)-Y*S(n)$ $\forall n.t2(n+1)=t2(n)+S(n)$ and assumption $\forall n.n<K\rightarrow L1=L2*t2(n)+t1(n)$ I want ...
0
votes
1answer
50 views

Reduce unable to solve simple inequalities with quantifiers

I have try to solve following inequalities using Mamthematica. But it unable to solve that. ...
2
votes
1answer
49 views

Substituting values of variables in solution of a system of linear equations

After solving a system of 21 linear equations in 21 variables (called Xi in my code) I got the values for all the 21 variables, in the following way: ...
-1
votes
0answers
37 views

Solving integral equation

I want to solve the following integral equation for $k$: $\left[\frac{\int_0^\infty e^{-ay}(1+y)^{C} dy}{\int_0^\infty e^{-ay}(1+y)^{C-1} dy}\right]-1=\int_0^\infty e^{-ay}(1+y)^{k} dy$ where $C$ ...
1
vote
0answers
23 views

Help Compiling Vectors using Iterations

So I have a nice code that runs properly, which I include below but, in my naiveté, I'm having issues iterating my procedure. Simply put, I have a function of two real variables $f(x,y)$ and I want ...
3
votes
1answer
73 views

Solve equation for a function as solution

I need to solve the following function: $$ h(z) = \sum^{40}_{k=0} \frac{k \, p(k)}{z- k \, h(z)} $$ where $p(k)$ is a probability distribution (in this case binomial with n = 40). Note that $h(z)$ is ...
1
vote
1answer
76 views

Solving two equations with modified Bessel functions

I am trying to solve two equations with Bessel functions in them, 1) C1*BesselK[0, 3.7268*10^-4*x] == 1.3*10^-6 2) ...
0
votes
1answer
31 views

Parameterize Subset of Complicated Zero Set

I recently asked this question: Evaluating Functions on Zero Sets (of other functions), and got fantastic assistance, but realized that there seems to be an extra issue when you're trying to ...
0
votes
0answers
24 views

Using the “reduce” function with s lot of equations and inequalities

I am using "reduce" to obtain all positive integers (plus 0) which satisfy a group of equations and inequalities. I have to automatize this procedure because I have to use "reduce" with at least 100 ...
0
votes
0answers
36 views

Matrix with equations as entries - how to choose them and solve them

I have a matrix in Mathematica, which I have built using Normal[SparseArray]. Each entry of this matrix is an equation in one variable. What I need to do is 1) to select some of the entries of the ...
0
votes
1answer
54 views

Arranging sides of an equation [duplicate]

I have to create my own function to solve equations (first and second degree). Assuming you have any input equation, how can I do to bring everything to the first side of the equation? Example. I ...
3
votes
2answers
103 views

Evaluating Functions on Zero Sets (of other functions)

I have a highly non-trivial function, call it $f(x,y)$, in which I want to look at its zero set in the $(x,y)$ plane, and plot/evaluate a different function $g$ precisely along this zero set. I have ...
1
vote
2answers
111 views

Find all the non-negative integer solutions of a linear equation

For the linear equation x[1] + x[2] + x[3] + x[4] + x[5] == n Is there any efficient way to find all the non-negative integer solutions of this equation when n ...
0
votes
1answer
54 views

Module output rules like Solve FindRoot etc built-in functions

How do I print rules {x -> values} as an output from my module? I'd like it formatted just like those from the built-in functions, so that users can use Out[ ] or % to directly apply the rules. ...
5
votes
0answers
48 views

Is there a way to tell how much time FindRoot is spending calculating Jacobians?

I am solving a large number of trascendental equations by scanning FindRoot over a bunch of seeds and a bunch of different parameter values, and I would like to ...
0
votes
1answer
68 views

Solution for Imaginary part of equation

I have a function Il12i[-0.001, -0.001, w, 0, 1, 0, 0.1002] which is depends on 1 variable w and it is real if w > -3666 (this number I found from graphs). This function is very complicated numerical ...
0
votes
0answers
28 views

Question about # Symbol [duplicate]

I am trying to solve an equation and the solution includes # symbols. I read up on them but can't understand how they are related to my solution. I solved a simple trigonometric equation of third ...