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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23 views

Manipulate parametters inside NSolve with complex variable

I think my question should be simple but I couldn't figure out a nice way to do it. I want to find zeros of a complex function (variable $z$) with real parameters ($\nu$, $\alpha$, $\xi$). My goal is ...
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1answer
59 views

FindRoot not obtaining solution for nonlinear system of log equations

There is a system of 9 non-linear equations, eq containing logarithms that I think it should be solvable numerically. There are a total of 9 variables with two of ...
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1answer
46 views

How to refer a solve answer to NDsolve [closed]

I don't know how to refer a solution of Solve to compute it in NDSolve, here's my code ...
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1answer
30 views

Read the graphic at another value

So I got this code and I'm new at coding, what I want to do is just read the graphic at a value of the Y axis and get the value of the X axis ...
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2answers
59 views

Obtaining the other axis value

I'm new at coding and I got this simple differential equiation and the plot of this function involved, I can obtain the value of the dependant variable based on the independant varible as usual, what ...
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1answer
235 views

How to solve vector equation?

Given the vector relation $(\mathbf{a}+3 \mathbf{b}) \perp(7 \mathbf{a}-5 \mathbf{b})$, $(\mathbf{a}-4 \mathbf{b}) \perp(7 \mathbf{a}-2 \mathbf{b})$, find the angle between $\mathbf{a}$ and $\mathbf{b}...
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2answers
56 views

Why these equations are not giving any solution? [closed]

I am trying to solve these three coupled linear equations but this gives me zero value. I don't know why it is happening. If anyone can resolve this is most welcome. ...
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1answer
42 views

NDSolve How do I insert another boundry condition

So I'm new to programming and I am trying to solve a very simple differential equation (i can do this by hand but the thing is i can't program it), the equation is ...
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39 views

Solving multiple equations with different values

I need to find x for this equation: a^x=b^x+c^x I import data by this commands: ...
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1answer
44 views

Find all valid triplets in this equation

I'm trying to find all positive integer triplets a,b,c that satisfy this equation. Note r is a constant. And 1 does exist: 23,13,121. Why is the result not found? Is there something wrong with the ...
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1answer
43 views

Solve an equation in mathematica without replacing the value of the parameter

Suppose I want to solve a simple equation in mathematica x-a=0.So I am writing the mathematica code for this as below: Solve[x - a == 0, x] So the output will be ...
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0answers
63 views

Solving a transcendental equation with some parameters

I'm trying to solve a transcendental equation: ...
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1answer
48 views

How can I solve my second order ODE? [closed]

I am trying to solve $\qquad y''(t)=\frac{1}{y(t)^3}-\Big(\frac{y(t)^4+1}{y(t)^5}\Big)y'(t)^2$ When I try to evaluate ...
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60 views

Solving a quintic equation [duplicate]

I am trying to solve the following equation in Mathematica: Solve[(xc - x) == 1/(xr - (x + x0)^2) + 1/(xr - (x - x0)^2), x] However, this yields ...
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2answers
311 views

How to ask Mathematica to solve a simple modular equation

What's the most straightforward way to ask Mathematica to find all solutions of an equation like $$3x + 2y + 4z = 0 \pmod {11}$$ (for instance), where either $x$, $y$, $z$ can be considered to be ...
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0answers
91 views

Real solutions of third and fourth degree equations

A few hours ago I "discovered" that if a third or fourth degree equation has distinct real solutions, it's possible to calculate them avoiding complex numbers. In particular, we have: ...
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1answer
82 views

Why does mathematica take a long time to solve this equation?

I want to solve an equation. By Mathematica, it take a long time. What the problem? Can anybody help me? The code is as follows: ...
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2answers
61 views

Unexpected results when plotting an output of Solve [closed]

My aim I want to find the solution of a cubic equation as a function of a parameter. In my code, the cubic equation is to be solved for the variable th with ...
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0answers
37 views

NSolve as integration limit

I need the (numerical) solution of equation to be integration limit as below. How to make it work? ...
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3answers
594 views

How can I get the center and radius of this circle?

I am able to make Mathematica plot the solution to a complex inequality as the interior or exterior of a circle : Let $a$ be a positive real constant, and $f(z) = \frac{z+1}{z-1}$. I want to get the ...
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1answer
89 views

Fastest way to compute the solution of this equation

I am looking for the solutions to the equation : $$a_1+...+a_n =x$$ with $$ -3 \leq a_i\in \mathbb {Z} \leq 3 \ \ \ \ \ \forall i$$ $$x \in \mathbb Z$$ Mathematica will get you the solutions ...
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1answer
67 views

Eliminating a variable with GroebnerBasis

I have the following two hefty equations: ...
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3answers
829 views

Is there the number `a, b, c, d, m` so that the equation has four integer solutions?

I am trying to find the integer numbers a, b, c, d, m so that the equation $$(x-a) (x-b) (x-c) (x-d) =m$$ where $a + d = b + c$ and $ m \neq 0$ has four integer ...
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0answers
56 views

If condition in differential equation

I need to plot the Integrate the Fire model of neuron. The differential equation is $\frac{dV}{dt} + \frac{V}{\tau} = \frac{I}{C}$. The initial condition is $V(0) = 0$. And there is this condition if ...
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1answer
30 views

Find root of function defined via NIntegrate

I have a function defined as ...
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1answer
54 views

Solve a set of equations in matrix form

I am trying to solve a set of equations in the form ui+vj=cij up until now I have done a rather complicated work around which is not entirely satisfactory. What I would like to do is to use the ...
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2answers
71 views

Mathematica 12 hangs up with specific powers p at Solve[{5 ==z-(Abs[-q]+Abs[q]), 3==z-(Abs[3^p-q]+Abs[3^p + q])}, {z, q}]. What should I do?

I try the code p = 7/22 Solve[{5 == z - (Abs[-q] + Abs[q]), 3 == z - (Abs[3^p - q] + Abs[3^p + q])}, {z, q}] when p=7/18 or ...
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24 views

NArgMin with Root functions

I'm trying to minimize an error function sumt to find some parameters S, s0, si : ...
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3answers
63 views

Algebraic solution from system of symbolic equations for single variable

I have a mathematical system like K_1 = c*h/d K_2 = b*h/c K_3 = a*h/b C = a+b+c+d h+d = W/h + b + 2a Constants: K_1, K_2, K_3, C, W Solve for: h, a,b,c,d Is it ...
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35 views

Assign Variable to NSolve

I'm looking to create an interactive region plot in Mathematica, and it's quite a complicated region (seen below).. The variable p is actually a function of y, and it's too hard to solve analytically. ...
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3answers
43 views

ND gives expression instead of number

I have a function sol defined as a solution to an equation (computed numerically). Specifically ...
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1answer
29 views

Solve::units: Solve was unable to determine the units of quantities that appear in the input

I'd like to solve the following two equations for P. But I'm getting "Solve was unable to determine the units of quantities that appear in the input.". Any suggestions on what could be the ...
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0answers
35 views

How to get a numerical result [closed]

I'd like to express a numerical value of h c/k T. The below does only show me the equation, but not the actual value. Any suggestions how I can achieve it would be greatly apprecaited. ...
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2answers
72 views

Why does Solve not solve these two coupled equations?

I have two simple coupled equations eqn1 = 0 == -x + P - G x (y + 1); eqn2 = 0 == -y + G x (y + 1); If I use ...
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34 views

Fit, NIntegrate in FindRoot results in non-numerical values

I'm trying to find certain values of q for which the derivative of the following function is equal to zero: ...
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1answer
129 views

How to reduce timing to find the integer numbers a, b, c, d, e, f, g, h, k, m of this equation?

I use by hand to get this result $$\sqrt{48+5 \sqrt{3}+\sqrt{27+4\sqrt{3}+\sqrt{12+3 \sqrt{3}+\sqrt{4+2\sqrt{3}}}}}=1+4 \sqrt{3}.$$ ...
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1answer
38 views

How I can use wolfram to solve 'x=atant, t=?' [closed]

x=atant, a is a constant, then t=? How to use wolfram to solve this equation?
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1answer
70 views

Solving set of equations having replacements

I am trying to solve a coordinate transformation problem which can be reduced to determining six parameters x1, x2...x6 in terms of two variable (phi and theta) satisfying the eleven equations (all ...
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2answers
34 views

NSolve - Problem with univariate long polynomial

Below I am trying to find the steady state of x1 (x2 is a func of x1) in terms of a variable q1. x1stst. Then I wish to compute q1 values giving "trace = 0&...
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1answer
67 views

NSolve doesn't compute with NIntegrate, just repeats input

First, I searched for similar questions but none of them helped me. I suppose that my problem has to do with a NIntegrate inside a ...
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1answer
32 views

N inside Manipulate: evaluating and showing roots of quartic in real time

Consider the parameterized quartic ...
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1answer
39 views

Why is NSolve finding different # of roots for algebraic function?

Consider roots of $f(u)=u^{-1/4}-2/15 u-1/6$ which can be written as $$ u^{-1/4}e^{-1/4 (2n \pi i)}-2/15 u-1/6=0 $$ where $u^{-1/4}$ is taken as principal-value. Or as a GroebenerBasis: $$ f(u)=-...
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1answer
52 views

How can I find in Mathematica if my equation have solution or not on a given interval?

I'm new to Mathematica. I usually used Wolfram Alpha; however, since the equation that I'm working with is a long equation I need to use Mathematica. This is an example of the problem. So, I want to ...
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0answers
45 views

Instability (quasi-randomness?) of results given by NDSolve [closed]

I am running on Mathematica 11.3 an unfortunately long NDSolve for Pontryagin principle (SIR epidemics), with both initial and ...
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1answer
77 views

NSolve for system of 14 non-linear equations

I am really new to Mathematica. Trying to solve the following system of equations (below). Get an error from Mathematica and have no idea what is the problem. Will very much appreciate any help. ...
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1answer
45 views

Solve error in multivariable equation

I have the code that works for one variable equation. However, when I modify it to include two coupled equations, solve gives me the error message which I do not understand. Below is the working code ...
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0answers
55 views

Solving partial differential equation

I am new to mathematica and I want to solve the following pde. I have two boundary conditions and one initial condition. I have tried the following code but the output is not the solution and it's ...
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0answers
38 views

NMinimize subject to many complicated conditions not obbeying imposed equation

This question derives from (and refers to) this one asked by me, and I hope that creating a new question rather than editing that one is appropriate. There I ask for a way to find the subset of the ...
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1answer
70 views

Does anyone here know how can we extract Lambda from the following equation

I am working on an estimation problem where I have the following Code is A = 1 + Pi*Csc[(1 + Pi)*\[Lambda]]^2* (Pi + Sin[2*(1 + Pi)*\[Lambda]]) Can anyone ...
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1answer
74 views

Why is my plot empty? [closed]

I'm trying to plot a PDE solution with this code: ...