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

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1answer
61 views

Missing solutions for complex equation system

I am currently working on a game-theoretic paper and trying to match two complex best response functions. The equation system includes two decision variables x and ...
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1answer
80 views

Why mathematica is not default set to give real solution, instead of complex one? [duplicate]

N[(-8)^(1/3)] gives 1. + 1.73205 i. Since $(-8)^{\frac{1}{3}}$ has three possible solutions, one real and other two are complex. So, why do not mathematica provides all the three solutions, and if ...
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1answer
97 views

solve recursive factorial function [closed]

Is there a way to solve this recursive factorial function? a[n + 1] = (n+1)*a[n], a[10]=10 I am looking for the value of a[n] ...
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1answer
90 views

Matrix elements scope definition

Alright, I'm very new to Mathematica and I have yet to learn a lot so please bear with me (sorry if this is a duplicate!): I want to create an $n\times n$ matrix $C$ with elements $c_{i,j}$ with $i,j ...
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1answer
69 views

How do I find the expression for where the first derivative equals 0? [closed]

I have a simple function of time. If I take the first derivative and set it equal to 0.0 I get the extrema of that function. I'm not interested in a numerical result, I want an expresion involving ...
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1answer
33 views

Error following a variable in an ODE [closed]

I am trying to solve a 4th order differential equation and this is my code thus far ...
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1answer
78 views

Strange functioning of RegionPlot with Reduce's output

I have defined this two quantities: f = (-b + Sqrt[b^2 + 4 a])/(2 a) g = (-b - Sqrt[b^2 + 4 a])/(2 a) and I want to solve this system in function of $a$, for ...
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1answer
136 views

Solving a System/Matrix of Equations in Matrix Form

Ok, I am trying to solve an equation involving matrices (well, tensors actually), which is of the form: $\mathbf{e}^{T} \cdot \mathbf{M} \cdot \mathbf{e}$ = $\mathbf{N}$, where $\mathbf{e}$ is an ...
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1answer
73 views

How to solve this equation?

Mathematica does not give me the correct solution (-1) for this equation: Solve[9^(x + 4) == 27^(1 - x), x] Do I miss something or is Solve the wrong approach ...
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2answers
134 views

Solving a two point boundary problem for a piecewise system of equations

I'm trying to solve a two point boundary value problem with a piecewise system of equations like: ...
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1answer
107 views

Fitting composed model to experimental data

I have mathematical model based on equation: $y(x) = 1 - \sum_{b=1}^{\inf} 2c_b \sin(c_b x/L) \exp(ax) $ (1), where $c_b$ are the positive roots of equation: $c_b \cot c_b + aL = 0$ (2). $L$ is a ...
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1answer
96 views

How do I link the txt file data sheet to mathematica and extract exact elements that I would like to use in solving for x? [closed]

I am trying to solve for a numerical solution for an equation which contains variables that evolves as index i incrreases. The actual equation that I am using to extract solution for x with an ongoing ...
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1answer
96 views

Find the solution of A^2+AB+B^2 = f(a,b,c) [closed]

I wanted to ask the following question: I need to find the solutions (a particular one is enough!) A and B of the equation $A^2 + AB + B^2 = (a^2+ab+b^2)(c^2+cd+c^2)$ How can I do it? Thank ...
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1answer
75 views

m equations and n variables. Reducing using Mathematica

I have six equations and thirteen variables. I would like to reduce it to seven free parameters. I used Reduce to solve it but it is taking really long (one full day and no output yet) and I think ...
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1answer
108 views

Numerically Integrating to find a Maximum using NDSolve

I am trying to numerically find an equilibrium (maximum) of a function using its differential. The following is a simplified version. ...
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2answers
82 views

Solve gives a solution which is contradicted by an example

I have the problem as described in the title. Here is the code: ...
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3answers
469 views

Mathematica Solve function does not solve double exponential

I am trying to solve: Exp[-a Exp[-x/b] - c Exp[-x/d]] == Y to x, and using the command ...
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1answer
89 views

FindRoot error, Solving equations [closed]

I'm trying to solve this problem but FindRoot function seem unable to find the root when r equals 4. ...
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1answer
342 views

Finding solutions of polynomials system

Let $f_1,...,f_n$ be a set of polynomials in $x_1,...,x_n$ with rational coefficients. I need to check whether a system $$f_1=a_1,...,f_n=a_n$$ has a real solution for large enough count of points. ...
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1answer
110 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 ...
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1answer
169 views

Solution of Coupled Second Order ODEs with Boundary Conditions

D[Tu1[x], {x, 2}] qu - Tu1[x] (fu0 + I w p) == Tou[x] f1 D[T1[x], {x, 2}] q - T1[x] (f0 - b g0 + I w p)== To[x] (f1 - b g1) - g1 For T1 , ...
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1answer
744 views

Why Mathematica can't solve this? NSolve or Solve

I want solution of x and y which should be positive real numbers ...
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1answer
186 views

What is most efficient way to convert system of equations to collection of functions?

I have the type of system M.x = b, where M is a known matrix and b is a known vector. M contains many parameters, call the entire parameter set 'a', so M => M[a]. I want to be able to efficiently ...
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1answer
156 views

invert system of two parametric ODEs and plot results of do-loop

I can solve this system of parametric ODE (u is the parameter,while g,e and ...
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1answer
140 views

Solve equations for all values of variables, rejecting certain types of solution

I have an expression, expr, containing 3 variables, 4 coefficients and 2 non-zero generic constants. I want to solve for the 4 coefficients such that the equation ...
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1answer
983 views

Green's Function in Mathematica

The equation I am trying to solve is: $$q \, T_1''(x)-T_1(x)(f-b \, g+i\,w \, p)=T(f_1-b \, g_1)-g_1\tag{1}$$ My professor says that $(1)$ can be solved by using Green's function $G(x,y)$, where ...
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2answers
221 views

Find the centre of FindGeometricTransform

I'm interested in using Solve[] to find the centre point of rotation (as an $x,y,z$ coordinate point) and axis of rotation (as a vector) from a ...
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1answer
154 views

I got wrong answers when solving an equation

I have this expression: ...
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1answer
189 views

Perform FindRoots on Function Evaluation Containing RootSearch

I am using Ted Ersek's RootSearch function in Mathematica 9.0 (http://library.wolfram.com/infocenter/Demos/4482/) to create a function that I am using for graphing. ...
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3answers
112 views

Applying Reduce[] to a table [duplicate]

I have a table for example: t = Table[k,{k,5}] which returns {1,2,3,4,5} and for every element in this table I want to check when it is $\leq 1 + a$. I ...
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1answer
516 views

Solving a nonlinear system of recurrence equations

I am having two problems regarding Mathematica, and both of them are happening because it does not accept such inputs: ...
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1answer
198 views

Defining a curved region for NDSolve

I have an equation to solve using NDSolve which involves two parameters: $en$ and $k$. The equation produces a set of curves when $en$ is plotted against $k$. In ...
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1answer
267 views

Plot the solution complex transcendental equation

I'm trying to plot an implicit function satisfying a complex transcendental equation. The code is the following: ...
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1answer
155 views

Minimum value with two factors

Approximate the minimum value of $2e^{x-2}-6x+xe^{x-2}$. Is my input correct? If not can you please correct it? ...
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2answers
346 views

How to pick a solution from a list of solutions using a test?

I have a list of solutions that depends on a parameter b3 and I'd like to get the solution for which the x value is minimal when ...
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1answer
224 views

Dsolve too slow — is there anyway around?

I am trying to solve: ...
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1answer
483 views

How to integrate this cumbersome piece-wise function?

I have this systems of equation: ...
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2answers
320 views

Error using Solve on Matrix Multiplication

I am trying to make a function the will find that value of $x$ in the following equation: $x.a=b$ all values of $x, a, b$ are matrices. The dimensions of $x$ are unknown, but $a$ and $b$ have the ...
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1answer
137 views

Problem about Solve

See this example : ...
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1answer
177 views

Changing ParametricNDSolveValue options for only part of the run

Here is an example of the system that I am running, ...
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1answer
145 views

FindMinimum gives wrong solutions inside a loop

I have a density function $\rho(r,z)$ and I want to calculate the minimum distance $d_{min} = \sqrt{r^2 + z^2}$ from the center (0,0) in which $\rho$ becomes negative. The easiest way is to find where ...
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1answer
111 views

Cannot Plot Output of Solve

I'm trying to plot the output of the following function t2[x_] in ...
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1answer
407 views

Stop Mathematica from giving imaginary solutions

I have the following equation: $$D=\frac{1}{64} \pi A ^3 B \sin \left(C\right)-\frac{1}{2} \pi A B \sin \left(C\right)$$ which I want to solve for $A$. The equation is cubic in $A$ so this should ...
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1answer
231 views

Finding parameters for first positive root of solution to differential equation to be equal to a desired value

I have a differential equation with parameters. The objective is to vary the parameters such that the first positive root of the solution is equal to a desired value ...
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1answer
87 views

How to get a solution involving logs in the right form?

How do I get Solve[(1/9)^(r/2) == 1/n , r] to give me Log[n]/Log[3] and not ...
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1answer
242 views

How to find 4 unknowns?

There are 4 unknowns constants: a,b,c,p. The variable is ...
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0answers
52 views

How can I improve the solution of my PDE?

I want to improve the last code to find a better solution for umi. For now I'm using only MaxStepFraction. Also, when I put no ...
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2answers
80 views

Plotting the solution of a cubic equation against a coefficient in the equation

I have to plot the solution of the following equation against the coefficient $L$. Since it's a cubic equation, I'd like to filter out the real solution first and plot that then. The equation is $L ...
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0answers
72 views

Can Mathematica Find Closed-Form Solution this Equation

I have tries to solve an equation by using Solve[] to find pl as a function of other variables. However, it generates an Error! Can anyone help? ...
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1answer
326 views

Usage of Piecewise/RSolve to solve an equation based on condition

I am trying to compute price of call option on a stock using the finite difference method. I have a VBA code for it, and I am trying to find out how I can use Mathematica memoization functions and ...