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

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2
votes
1answer
128 views

Symbolic quadratic constrained maximization with non-negativity constraints?

Dear Mathematica users, I attempted to maximize the below quadratic function K, subject to x1+x2<=A, and a series of ...
-1
votes
2answers
164 views
11
votes
8answers
482 views

Find the minimum integer r such that $(10^r - 1)/37$ is an integer

I know Element[(10^r - 1)/37, Integers] tests the condition. So what is the command that gives me the minimum integer value r ...
7
votes
3answers
439 views

Implement the Bisection algorithm elegantly and easily

Description: Rencently, I have finished my course Numerical Analysis, so I'd like to implement many algorithm that I have learned from that course.By this practice, I hope that I can improve my ...
0
votes
2answers
94 views

Obtaining the relations of variables using diagonal matrices

I know this is too an elementary question, but I am a pathetic newbie in mathematica and I cannot find any answer by googling. What I want is obtaining some relations of unknown variables using their ...
0
votes
1answer
87 views

Solve with limit over multiple variables

Very new to Mathematica so apologies for what is probably numpty question. The following returns no solutions. However, there is a solution! If I set a = 1 I get the solution b = 1/2. Can you explain ...
0
votes
0answers
82 views

solving singular matrix [duplicate]

Hello I have a matrix that is singular, and i wanted to use linear solve to solve it but that doesn't work with mathematica. The matrix given as a list looks like this: ...
4
votes
2answers
169 views

Specifying and solving a PDE on an L-shaped domain

I wish to solve Laplace's equation with Dirchlet boundary conditions on an L-shaped domain as described here http://www.inf.ethz.ch/personal/tulink/FEM14/Ch1_ElmanSyvesterWathen_Ox05.pdf I know how ...
2
votes
1answer
104 views

Optimizing alphametrics code

First of all, thank you all in this great community. I have been reading a lot of threads about Mathematica optimization learning things like using Compile ...
0
votes
0answers
39 views

Plotting the real positive solution to a parametric equation [duplicate]

I have the following parametric equation $$ x^2-a=0 $$ where $a$ is a given parameter. I would like to plot the nonnegative real root ($\sqrt{a}$) using NSolve as $a$ varies from $0$ to $1$. Can ...
-3
votes
2answers
170 views

Why does this function inside FindRoot fail to evaluate?

Can someone help me understand why function mu found below does not execute when everything before it seems ok. ...
0
votes
0answers
86 views

How to assign equation solutions to variables [duplicate]

I have 12x12 Matrix with which I have to solve the equation below: ...
0
votes
1answer
62 views

Searching in parameter space for a given number of solutions

I have this problem : I have some function g[a,b;x], where a,b are parameters and x is a variable. I know (graphically) that an equation g[a,b;x]=0 has zero, one or two solutions. I want to keep 'a' ...
0
votes
0answers
73 views

Solving a set of equations

I have x = {1, ..., 10} and y = {11.33, 12.63, 12.08, 11.17, 10.24, 9.41, 8.67, 8.02, 7.45, 6.96}. I am trying to fit a model ...
1
vote
0answers
141 views

Equation Solving

As I stated in this question I want to solve a series of equations while setting some rules such as q[2]->1 or q[2]->3*10^-4. However, what should I do if I want to set another rules to my input? I ...
0
votes
1answer
96 views

Non Linear Equation Solving with Matrices

Suppose I have the following matrix equalities: A=X, B=Y where the left-hand side matrices are numeric and the right hand side contains non-linear combinations of unknowns. Since I have quite a few ...
1
vote
0answers
264 views

NDSolve: Equation with interpolating function [closed]

I have a question regarding DSolve and NDSolve functions in Mathematica 10. For instance, I'd like to solve an ODE: ...
0
votes
0answers
65 views

How to find only the negative Imaginary solutions and positive Real solutions?

Following this post Help Please : Error in plotting the solutions of FindRoot , I want to plot only the negative Imaginary solutions Wi(K)<0 and positive Real solutions Wr(K)>0. Please, how do it? ...
0
votes
1answer
54 views

Finding a solution when there are two piecewise functions at play

The goal is to mathematically figure out where is the point when the both of the diagrams are the same distance to the Y-axis. The solution to such a problem can be obtain quite easily by just ...
2
votes
0answers
127 views

Apart for complex roots?

Let p[x] be a polynomial in x and consider the partial fraction decomposition of 1/p[x]. ...
0
votes
1answer
83 views

Solving A Series of Equations

I want to find the solutions of a series of equations as I stated in this question before. I understood how to solve the equations by maximizing the value of a variable but now I want to find the ...
0
votes
0answers
76 views

Is it possible to get a symbolic expression from FindRoot?

I need to have an expression where the solution from FindRoot (or another solver) depends on one or more parameters. Let's say I have a polynomial of second ...
0
votes
0answers
49 views

Order of evaluation when using Solve and Minimize

I have to solve numerically an integral, that ends up being more or less as follows: Solve[f[x]==a*Sum[Sin[x-i]*(f[i]-f[i-1]),{i,1,x}],f[x]] (not actual ...
1
vote
2answers
453 views

How to obtain all solutions for Cos[x] Cosh[x] == 1?

Both analytical solutions or all numerical solutions are good enough. FindRoot may be a possible solution, any better solution? ...
0
votes
0answers
61 views

when DSolve fails

I am doing this mathematical problem $c*G_{vv}+ d*G_{u} + e*G_{v} +f*G=0$, where $c, d, e$ and $f$- are constant coefficients. I already know that this is second order PDE and we classify it by ...
1
vote
1answer
118 views

strictly positive solution to $Ax=b$

How to find in mathematica one real strictly positive solution, if any, of $Ax=b$. A is rectangular matrix. Thanks
0
votes
1answer
92 views

Find all roots of a system of non-linear equations [closed]

Suppose I have a list of non-linear equations, and FindRoot returns different answers depending on where I start. I'm new to Mathematica. What is the best practice in mathematica for establishing all ...
2
votes
1answer
156 views

Seeking simple function in interval

I am a bit rusty, and struggling to solve this problem. Looking for a simple, well behaved parametric function f[t], from [0,1] to [0,1] such that: f[0] = f0; f[1] = f1; f'[1] = ff1; where -1<= ...
1
vote
2answers
121 views

How to find roots of a system of equation when number of equations and variables don't match?

I'm trying to check if a system of equations has a solution around a given point, the problem is that I'm using FindRoots and doesn't work when there are a different number of equations and variables, ...
1
vote
1answer
100 views

Numerical solution of two equations in two functions

I would like to obtain a solution to the following two equations ...
0
votes
1answer
88 views

Mathematica answers `Solve[Integrate[f, x] == x^4, f]` wrong [closed]

The input Solve[Integrate[f, x] == x^4, f] ouputs {{f -> x^3}} Why?
0
votes
1answer
100 views

In which condition releated to thee coefficients some equation has a solution

Please excuse me if the question seems to commonplace. Can Mathematica give a response to this question: In which condition related to the coefficients $c>0, \, n\geq 2, 0<p<1,\, a>c$ ...
0
votes
0answers
40 views

Solve fails when another term added to an equation

These equations take 2 minutes for my computer to solve: ...
4
votes
1answer
264 views

How to solve this Integral equation

D[x[t] - x[t - 1]/(2 E), {t, 3}] + Integrate[E^(-δ)*x[t - δ]/5^t, {δ, 2, 2.5}] == 0 I found solve this problem is hard with Mathematica. I also find a article ...
0
votes
1answer
117 views

How to put constraints on NDSolve[] solution

Assumed the following example of double pendulum by Thison (Answered by Jens): Animation of double pendulum Imagine that in the given animation(i.e. http://i.stack.imgur.com/p4TgL.gif ), the second ...
-1
votes
1answer
98 views

How to “Control” the Type of Solutions Mathematica Produces Using the Solve Function

Given multiple fractions I am using the Solve function to find the values of the variables $x[1],\ldots,x[7]$ such that the numerator and denominator of each fraction are both 0. I usually have ...
1
vote
1answer
539 views

This system cannot be solved with the methods available to solve

I know questions about this warning have been posted a thousand times over. But I really couldn't find any solution that worked in my case. It's quite simple: ...
0
votes
2answers
67 views

NSolve gives {{ x -> #}}, How do I make x = #; I need to use the x value again later

I want to use: demand = {1.92, 2.07, 2.37, 2.72, 2.87}*10^6; NSolve[SetV == demand[[1]]/(Cpf (1 - χ)), χ] I want to make a vector of solutions ...
0
votes
2answers
130 views

Systems of equations

As I stated in this question I am trying to find the roots of a set of equations. I followed the instructions that the answer gave me and Mathematica gave me the solutions. 1- However whenever I try ...
2
votes
0answers
137 views

What are the steps using boolean algebra for transforming one equation into another?

I have a special case where I have two equations, which I have solved in a better and quicker way, but I need to solve with Boolean algebra. Using the laws of Boolean algebra, I have to prove that ...
1
vote
1answer
112 views

How To Replace $\rightarrow$ by $==$ in Mathematica's Output when using Solve

I want to create equations out of the output (solutions) produced by Mathematica when using the Solve functions. For argument's sake, consider the following. ...
2
votes
1answer
85 views

Multiple dynamic equations for plotting?

Say I have a bunch of equations between variables e.g. h=bcd, i=hce, j=ihbd, ...
2
votes
0answers
176 views

Fitting an implicit function to data with error bars [closed]

I am trying to fit a Brillouin function to the peak intensity of neutron scattering data, for which I have an error bar for each data point. For this the program has to fit a function, for which the ...
1
vote
1answer
86 views

Non-linear system of equations with a parameter

I want to solve k*x-(x-y)*y^2==0 and y+(x-y)*y^2-(1-x-y)==0 for -10 < k <10 How ...
3
votes
1answer
108 views

Solving simultaneous systems of linear equations

I have several systems of linear equations in matrix form, and I would like to find the $\vec{x}$ that simultaneously solves them: $$A_1\vec{x} = b_1$$ $$\vdots$$ $$A_n\vec{x} = b_n$$ Is there a ...
2
votes
0answers
89 views

How does Mathematica resolve symbolic systems of inequalities?

Before getting into my (probably annoying) question, let me provide some context: I recently started using Mathematica to automatically perform stability analyses that I previously did by hand. A ...
3
votes
1answer
209 views

Solving a large system of nonlinear equations

I have a system of 80 nonlinear equations with 64 variables to solve in Mathematica but it takes a lot of time (about two hours) and then it return "no more memory available" knowing that I have 8GB ...
2
votes
1answer
175 views

Catastrophic loss of precision

while I am trying to solve the double integral in the range of 0 to Infinity (for both the integral) it give me the error Catastrophic loss of precision in the global error estimate due to ...
2
votes
2answers
201 views

cycloid parametric [closed]

How do I enter 3 parametric equations for cycloids corresponding to circles with radii 1, 2, and 4. I have tried ...
0
votes
1answer
83 views

How to re-express solution to system of equations after truncating the solution at a given order to give an exact answer

I have a simple enough system of two equations that need to be inverted: ...