Questions tagged [equation-solving]

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

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14 views

Decomposing polynomial as a sum of polynomials multiples of two polynomials

Suppose that I have a polynomial $f(s,t)$ with coefficients in $R=\mathbb{R}[x_{1},\dots, x_{n}]$ and in the variables $s,t$ and I know that $f(s,t)$ can be expressed as $(s-t)f(s,t)=p(s,t)h(s)+q(s,t)...
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25 views

Solve Matrix equations with Cross Product: weird system of equations

I would like to find the values {Pfx, Pfy, Pfz} that satisfy the equation A X B = C . The code of everything is at the end, I want to ilustrate with images what i think of first: A is this: B is this:...
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1answer
40 views

Solving abstract factorization problem with Mathematica

I'm a Mathematica newbie. Given something like: $$(r_0 + r_1 a + r_2 a^2 + r_3 a^5)(r'_0 + r'_1b + r'_2 b^2 + r'_3 b^5) = 1 - a^5 b^5$$ I'd like to determine if there exist $r_i,r'_i$ that solve the ...
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1answer
72 views

Solving an ordinary differential equation with boundary condition at infinity

I want to solve the following differential equation f''[z] + (1/z)*f'[z] - f[z] + f[z]^3 == 0 subject to the boundary conditions $$f^{\prime}(0)=0\qquad\lim_{z\to\...
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57 views

Is there an alternative to Reduce that can solve this system of inequalities? [closed]

I try to find the eventual root of a function depending on several parameters. ...
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29 views

can not replace when use ctrl+f

I have a very long output, therefore, I want to find and replace some repeated expressions with abbreviations using crtl +f in Mathematica. when I enter expressions, the mathematical can find it and ...
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1answer
47 views

Numeric solution of ODEs oscillates strongly and stops halfway?

I tried to reproduce the results of a paper. The differential equations are given by ...
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1answer
40 views

NSolve missing solutions

I'm having trouble solving the transcendental equation. For some values ​​of bi, NSolve obtains 6 roots, however when changing the value, it obtains 5. Graphing the function clearly shows that the ...
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42 views

Why doesn't Reduce work?

I try to solve an inequality with parameters using Reduce. The answer i get is : This system cannot be solved with the methods available to Reduce. Here is the inequality: ...
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2answers
73 views

Forcing mathematica to solve polynomials exactly

It used to be the default behavior that Mathematica would solve polynomials of degree 4 exactly. In the current version I have (12.2.2.0) it sometimes gives numerical answers. Is there a way to change ...
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1answer
54 views

Solve yields complex Root even if the domain is Reals

I want to solve $x^3=a^2$ for $x$ where $a>0$ and $x$ is real. The answer I want is $$x=a^{2/3}.$$ On Wolfram Cloud, I tried ...
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1answer
40 views

Numerically obtaining roots as a function of another variable

I have an equation $f(x,y) =0$ that Mathematica can solve numerically using NSolve for a fixed $y$. I want to perform the following operation: ...
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31 views

Solve coupled equations in the steady state

I want to solve 16 coupled differential equations in the steady state. Among the answers, I only require two of the answers. But the Mathematica does not show me the answers in detail!!! Can anybody ...
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1answer
60 views

Solve equation system for expression [closed]

How to solve this equations and find specified expression (all integers)? x * N + y = 2012 y * N + x = 2011 x + y = ? I've tried but got formulas as an answer ...
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1answer
36 views

Matching polynomial coefficients when solving an equation

Two polynomials of the same degree are equal if the they have the same coefficients. I would like to use that to find all coefficients of a polynomial: ...
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1answer
37 views

Solve gets stuck with rater simple algebraic equation

Solve[(a^(1/4) + c^(5/3) x)^(6/5) == b && a > 0 && b > 0 && c > 0, x, Reals] is running forever. Why?
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1answer
94 views

NSolve V12.1.1 much slower than V6.0 for the same polynomial system

We are solving polynomial systems with real coefficients using NSolve. A typical system is attached below. The problem we have is that Mathematica V12.1.1 solves it 17 times slower than V6.0, see the ...
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1answer
33 views

Solve equation with four variables [closed]

I am trying to solve the following equation with mathematica $0 = \frac{(2n+1)}{w^2} + \frac{(2n-1)}{w^2}x^2 + 2\frac{z}{y}\frac{x}{w}$ where $n$ is just a positive integer. So I used the following ...
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2answers
169 views

How can I remove constants from a reduced result?

I am trying to reduce some equations and get the final simplified answer. But there are two issues. This is just an example to show what my problem is. There are lots of similar samples with the same ...
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1answer
43 views

3D plot using Table & FindRoot

I have two expressions involving terms $S_1$ and $S_2$, call the expressions $F1, F2$. I cannot solve $F_i=1$ for $S_i$ so instead I numerically approximate using ...
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1answer
55 views

Modulus option quietly nerfed for Solve?

Recently asked my students to put together something like this: Reduce[x^2 ==b, b, Modulus -> 11] For me, on 12.1, this gives: ...
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2answers
99 views

Finding the coefficients of an expression

I have a set of formulas of the following form: ...
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0answers
50 views

Solving these set of equations with complex parameters

For $\{a,b,c\}\in \mathbb{C}$ and $\{\gamma,N\}\in \mathbb{Z}^+$, I have an equation ...
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1answer
48 views

Conically shaped pit

I need help with b. I tried to use the find root but it didn't work !
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39 views

Solve gives an empty output

I want to solve the following system, but it gives me an empty output: ...
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1answer
88 views

Why Mathematica is returning a complicated output rather than a simple one (as in the screenshot) [closed]

I am using Nsolve to get output on my thread of equations. I have two screenshots attached here. I was supposed to get the same result as pic#1, rather than pic#2. Can someone help me with how can I ...
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2answers
91 views

Does a positive real solution exist to this problem?

I wrote the following code for getting the solution. I am not sure if the code I wrote is correct. The problem is further intensified by the fact that I don't know if a solution exists to this problem ...
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52 views

Solve not giving a solution for given variables

Solve is not giving me a solution for the following: ...
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1answer
153 views

Running Mathematica in 'SpouseMode'

In this previous question I looked into a deprecated capability of Mathematica from Version 2. Mathematica command that allows it to read my intentions Thanks to all for your answers. I note that ...
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1answer
35 views

How can I solve equations by matching prefactors?

I have complicated expressions involving traces, for example tr[a], tr[a^2], tr[a]^2, ...
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0answers
37 views

NSolve with ParametricFunction

I have solved a SDE with ParametricNDSolve: s = ParametricNDSolve[ {p1, m1, p0, m0}, {P, m}, {r, 0, 1}, {m, k, e, Cnew} ] And now I want to treat the ...
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0answers
43 views

NDSolve gives error with solving given equation [closed]

I need to solve differential equation, but I am not sure what is wrong with it, because Mathematica does not want to solve it and gives me ...
2
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1answer
20 views

How can I control the following behavior of Reduce?

Consider the following 3 lines of code: ...
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1answer
27 views

Using NSolve with an interporlated function

I have defined the interpolation function below ...
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2answers
85 views

How do you overcome recursion limits when using DSolve?

I have the following program to solve for the neutron to baryon ratio during BBN. I've replaced many of the derived values with constants in order to focus on the problem: ...
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95 views

NDSolve big system non linear coupled ODE's Method Residual Stiff System

I'm trying to develop a continuous time unscented Kalman filter for a dynamic system inspired to this article: "On Unscented Kalman Filtering for State Estimation of Continuous-Time Nonlinear ...
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2answers
104 views

Solving rectangular plates vibrations wave equation

I am a new Mathematica user (about 6 month) and I am trying to solve the wave equation for a rectangulare plate (not an elastic mebrane). I read some papers about this subject and my code structure is ...
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1answer
33 views

Difficulty in evaluating the constants of simultaneous equations

How to find the constants A1, A2, B1, B2 using linear solve or null space function in Mathematica. ...
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1answer
112 views

Solving time dependent Schrodinger equation for a wavefunction and harmonic oscillator [closed]

How can I obtain a GIF/graph similar to these ones here by solving the time-dependent Schrodinger equation $$ i\hbar\frac{\partial ψ(x,t)}{\partial t} = -\frac{\hbar^2}{2m}\nabla^2ψ(x,t) + V(x)ψ(x,t)$$...
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1answer
60 views

How to solve two implicit functions with two variables and parameters

I have two functions given as; u[c_,d_] := Sinh[a b^2 c^2 + 3a b d] and v[c_,d_] := Log[a b^2 c^2 + 3a b d + d^2] - d. I want ...
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2answers
44 views

Manipulating equations into a certain form

I am a newbie in Mathematica, and I want to know how to manipulate and derive an equation. The equation I want to obtain is as shown on the image. I've tried Solve, Simplify, FindRoot, Expand, Reduce ...
2
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1answer
57 views

Solve returns a couple of wrong solutions to a nonlinear equation

I am trying to understand what is wrong with the line Solve[c^2*α - c*α*(c + Sqrt[c^2 + 4])/2 + 1 == 0, c] which returns ...
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1answer
50 views

How to use Solve to isolate one variable in equation?

I have x = 1 - 1/2/y^2 - 1/y/Exp[y^2]/Sqrt[Pi] I would like to write $y$ in terms of $x$ and I know $x$ is real. I tried ...
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0answers
41 views

Eigenvalues of a 6x6 matrix [duplicate]

Eigenvalues[{{0, A, 0, B, 0, D}, {-A, 0, -C, 0, -EE, 0}, {0, C, 0, A, 0, B}, {-B, 0, -A, 0, -C, 0}, {0, EE, 0, C, 0, A}, {-D, 0, -B, 0, -A, 0}}] I am ...
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1answer
41 views

Changes When Using Solve with Plot3D and Evaluate

I'm solving the following equation, which should be straightforward: ...
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1answer
122 views
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1answer
36 views

How to solve this equation with respect to P?

I would like to solve it for P when Q=0. I know it can be done by "FindRoot/Reduce" commands. But for that, I would have to assign numerical values to all the characters except P. I don't ...
3
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2answers
133 views

Mathematica crashing on Solve (finding points on 4 circles on a sphere). How to reformulate?

I define a small circle on a unit sphere by the direction of the plane's normal and its distance to the sphere center (i.e. origin) like this (parametrized by the angle t): ...
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1answer
41 views

Trouble trying to find solutions for linear equations with FindInstance?

I am trying to do the following: Given $x=i+\sqrt{3}$, finding a polynomial $p$ with rational coefficients not all zero such that $p(x)=0$. For this, I am doing the following: ...

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