Questions tagged [equation-solving]
Questions on the analytic and numerical equation solving functions of Mathematica (Solve, Reduce, NSolve, FindRoot, DSolve, RSolve, etc.).
5,032
questions
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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)...
-2
votes
0answers
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:...
0
votes
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 ...
1
vote
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
$$f^{\prime}(0)=0\qquad\lim_{z\to\...
0
votes
0answers
57 views
Is there an alternative to Reduce that can solve this system of inequalities? [closed]
I try to find the eventual root of a function depending on several parameters.
...
0
votes
0answers
29 views
can not replace when use ctrl+f
I have a very long output, therefore, I want to find and replace some repeated expressions with abbreviations using crtl +f in Mathematica. when I enter expressions, the mathematical can find it and ...
2
votes
1answer
47 views
Numeric solution of ODEs oscillates strongly and stops halfway？
I tried to reproduce the results of a paper.
The differential equations are given by
...
0
votes
1answer
40 views
NSolve missing solutions
I'm having trouble solving the transcendental equation. For some values of bi, NSolve obtains 6 roots, however when changing the value, it obtains 5. Graphing the function clearly shows that the ...
0
votes
0answers
42 views
Why doesn't Reduce work?
I try to solve an inequality with parameters using Reduce.
The answer i get is :
This system cannot be solved with the methods available to Reduce.
Here is the inequality:
...
0
votes
2answers
73 views
Forcing mathematica to solve polynomials exactly
It used to be the default behavior that Mathematica would solve polynomials of degree 4 exactly. In the current version I have (12.2.2.0) it sometimes gives numerical answers. Is there a way to change ...
3
votes
1answer
54 views
Solve yields complex Root even if the domain is Reals
I want to solve $x^3=a^2$ for $x$ where $a>0$ and $x$ is real. The answer I want is
$$x=a^{2/3}.$$
On Wolfram Cloud, I tried
...
0
votes
0answers
23 views
How to Constrain the arguments of the logs to be positive, in order to solve this inequation? [closed]
I need to solve this inequality:
...
1
vote
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:
...
0
votes
0answers
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 ...
0
votes
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 ...
1
vote
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:
...
0
votes
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?
1
vote
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 ...
0
votes
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 ...
4
votes
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 ...
0
votes
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 ...
1
vote
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:
...
3
votes
2answers
99 views
1
vote
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
...
-3
votes
1answer
48 views
0
votes
0answers
39 views
Solve gives an empty output
I want to solve the following system, but it gives me an empty output:
...
2
votes
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 ...
2
votes
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 ...
0
votes
0answers
52 views
Solve not giving a solution for given variables
Solve is not giving me a solution for the following:
...
7
votes
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 ...
1
vote
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, ...
0
votes
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 ...
0
votes
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
votes
1answer
20 views
0
votes
1answer
27 views
1
vote
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:
...
2
votes
0answers
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 ...
1
vote
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 ...
1
vote
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.
...
1
vote
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)$$...
0
votes
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 ...
0
votes
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
votes
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
...
0
votes
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
...
1
vote
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 ...
0
votes
1answer
41 views
Changes When Using Solve with Plot3D and Evaluate
I'm solving the following equation, which should be straightforward:
...
0
votes
1answer
122 views
0
votes
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
votes
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):
...
1
vote
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:
...
