Questions tagged [equation-solving]
Questions on the analytic and numerical equation solving functions of Mathematica (Solve, Reduce, NSolve, FindRoot, DSolve, RSolve, etc.).
4,954
questions
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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 ...
2
votes
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 ...
-1
votes
0answers
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 ...
3
votes
0answers
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 ...
1
vote
1answer
45 views
2
votes
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 $t_f$ ...
0
votes
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 ...
0
votes
0answers
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 ...
1
vote
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
$$ -4<a_i\in \mathbb{Z}<4$$
$$ -7<b_i\in \mathbb{Z}<7$$
$$ -4&...
2
votes
2answers
66 views
Solving a recursive equation iteratively (including PolyLog function)
I have the following equation which I want to solve:
$$
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 ...
1
vote
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
...
0
votes
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 ...
0
votes
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 ...
0
votes
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
...
1
vote
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
...
2
votes
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 ...
4
votes
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}...
0
votes
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.
...
1
vote
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 ...
0
votes
0answers
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:
...
1
vote
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 ...
0
votes
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 ...
1
vote
0answers
61 views
Solving a transcendental equation with some parameters
I'm trying to solve a transcendental equation:
...
0
votes
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
...
0
votes
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
...
2
votes
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}$$
(for instance), where either $x$, $y$, $z$ can be considered to be ...
1
vote
0answers
69 views
Real solutions of third and fourth degree equations
A few hours ago I "discovered" that if a third or fourth degree equation has distinct real solutions, it's possible to calculate them avoiding complex numbers.
In particular, we have:
...
0
votes
1answer
80 views
Why does mathematica take a long time to solve this equation?
I want to solve an equation. By Mathematica, it take a long time. What the problem?
Can anybody help me?
The code is as follows:
...
0
votes
2answers
59 views
Unexpected results when plotting an output of Solve [closed]
My aim
I want to find the solution of a cubic equation as a function of a parameter. In my code, the cubic equation is to be solved for the variable th with ...
0
votes
0answers
36 views
NSolve as integration limit
I need the (numerical) solution of equation to be integration limit as below.
How to make it work?
...
7
votes
3answers
582 views
How can I get the center and radius of this circle?
I am able to make Mathematica plot the solution to a complex inequality as the interior or exterior of a circle :
Let $a$ be a positive real constant, and $f(z) = \frac{z+1}{z-1}$. I want to get the ...
1
vote
1answer
89 views
Fastest way to compute the solution of this equation
I am looking for the solutions to the equation :
$$a_1+...+a_n =x$$
with
$$ -3 \leq a_i\in \mathbb {Z} \leq 3 \ \ \ \ \ \forall i$$
$$x \in \mathbb Z$$
Mathematica will get you the solutions ...
6
votes
0answers
671 views
Determine if x^3+y^3+z^3+t^3 = 10^2021 has a solution [migrated]
I want to know if the equation $x^3+y^3+z^3+t^3=10^{2021}$ has distinct positive integer solutions
PowersRepresentations[10^2021, 4, 3]
return
...
3
votes
1answer
63 views
5
votes
3answers
819 views
Is there the number `a, b, c, d, m` so that the equation has four integer solutions?
I am trying to find the integer numbers a, b, c, d, m so that the equation
$$(x-a) (x-b) (x-c) (x-d) =m$$
where $a + d = b + c$ and $ m \neq 0$ has four integer ...
1
vote
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
votes
1answer
30 views
1
vote
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
vote
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 ...
0
votes
0answers
24 views
NArgMin with Root functions
I'm trying to minimize an error function sumt to find some parameters S, s0, si :
...
4
votes
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 ...
0
votes
0answers
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. ...
-1
votes
1answer
55 views
Cannot find nilpotent elements for Tessarines [closed]
Entering the following system returns only a trivial solution (zero):
...
2
votes
3answers
41 views
ND gives expression instead of number
I have a function sol defined as a solution to an equation (computed numerically). Specifically
...
0
votes
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 ...
1
vote
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.
...
1
vote
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 ...
0
votes
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
votes
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}.$$
...
1
vote
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?
