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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How to do deconvolution

I have these 3 equations: Now I want to calculate the function f(x). The f(x) should like this: Here a1-a7 are constant parameters. Could someone tell me how to calculate the f(x)? Thank you very ...
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0answers
28 views

How to change the size of the y axis

I got this code but the solution is very tight in the Y axis, I wanna know how can I change the scale or the size of the Y axis and how can I obtain its solution cause it's not as simple as ...
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62 views

Solve a system consisting of inequalities and equations with lots of variables

As the code shown below, I use FindInstance to find a set of real parameters which satisfy the 5 equations and 7 inequalities. Since there are lots of parameters, I didn't get any answer from ...
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26 views

Numerically solve a non-differential equation with InterpolatingFunction as output

I have some a function that I need to solve numerically over an entire domain (Ideally I would like an InterpolatingFunction object as output), which does not include any derivatives. I have found a ...
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1answer
45 views

How to make FindRoot work with PolyLog functions

I have the following code: ...
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2answers
102 views

Minimization using NMinimize

I have a system of ODEs say $$x'(t)=2 x(t)-x(t)y(t)-3 x(t) g(t),$$ $$y'(t)= y(t)-2 x(t)y(t)- x(t) g(t)$$ with ICs $x(0)= 1, y(0)=1/2$, say, for $t_0 \leqslant t \leqslant t_f$, where $t_0$ and $t_f$ ...
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1answer
77 views

Can NDSolve be used for a system with number (+40) of equations?

I have 42 coupled differential equations (6 of them are PDE's). My system has 6 objects and an object have 7 coupled equations. Since these objects are interacting with each other, their coupled ...
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16 views

How to force N[ ] to output the real value (or all values) for negative cube roots [duplicate]

Evaluating N[(-1)^(1/3)] returns 0.5 + 0.866i in my v12.0 notebook. Of course, the equation x^3 = -1 has three distinct solutions for x. Is there a global (or local) option that will force Mathematica ...
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1answer
25 views

Is there a better way : solutions to integer equation

I have the following code which solves for Integers the equation $$a_1+a_2+a_3+a_4+b_1+b_2+b_3+b_4+c_1+c_2+c_3+c_4=tot$$ with $$ -4<a_i\in \mathbb{Z}<4$$ $$ -7<b_i\in \mathbb{Z}<7$$ $$ -4&...
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2answers
66 views

Solving a recursive equation iteratively (including PolyLog function)

I have the following equation which I want to solve: $$ I_D = [Li_2(-e^{V_D-I_D})-Li_{2}(e^{I_D})] $$ Here $Li_2(x)$ is the PolyLog function of order $2$. Is there a way to solve this equation ...
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1answer
53 views

Finding the joint domain for a couple of functions of three variables

I have two functions $f_{1}(x,y,z)$ and $f_{2}(x,y,z)$ defined respectively as ...
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1answer
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
57 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
29 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
58 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
213 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
41 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
41 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
61 views

Solving a transcendental equation with some parameters

I'm trying to solve a transcendental equation: ...
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1answer
47 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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0answers
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
298 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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69 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
80 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
59 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
36 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
582 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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671 views

Determine if x^3+y^3+z^3+t^3 = 10^2021 has a solution [migrated]

I want to know if the equation $x^3+y^3+z^3+t^3=10^{2021}$ has distinct positive integer solutions PowersRepresentations[10^2021, 4, 3] return ...
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1answer
63 views

Eliminating a variable with GroebnerBasis

I have the following two hefty equations: ...
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3answers
819 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
51 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 ...
2
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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
51 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 ...
1
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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
62 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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33 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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1answer
55 views

Cannot find nilpotent elements for Tessarines [closed]

Entering the following system returns only a trivial solution (zero): ...
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3answers
41 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
26 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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1answer
35 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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0answers
31 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: ...
7
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1answer
122 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
37 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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