# Tagged Questions

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

1answer
298 views

### Can Mathematica solve functional equations with nested variable?

First, inline free form input can solve these equations: But it seems no native Mathematica function can solve these, there is even an error page for equations of this form (nestdv). Now my ...
1answer
51 views

### How can I choose the coeffcients so that the givent system of equations has four integer solutions?

Consider the system of equations with unknown are $(x,y)$. $$\begin{cases} a_1x^2+b_1y^2 + c_1xy+d_1x + e_1y+f_1=0,\\ a_2x^2+b_2y^2 + c_2xy+d_2x + e_2y+f_2=0. \end{cases}$$ I want to find the ...
1answer
78 views

### Finding roots of Bessel function $y=3J_1(x)+xJ_1'(x)$ is returning inaccurate roots. Not Kernel bug [closed]

I can't figure out why Mathematica is returning the incorrect roots. The first five should be 2.9496,5.84113,8.87273,11,9561, and 15.0624 according to my textbook. ...
1answer
91 views

### How to efficiently find only the rational roots of a rational complex polynomial?

I need to find all the rational roots of a bunch of high-order polynomials with rational complex coefficients. Is there an efficient way to do this? My best effort on an example polynomial: ...
1answer
104 views

### Does Solve[] find ALL the exact roots of rational polynomials?

Does Solve[] find ALL the exact roots of rational polynomials? I've done a bunch of tests where I created an expression with some analytic roots, and Solve[] always found them all. But is the ...
1answer
239 views

2answers
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### I'm trying to solve a system of complex equations

I'm simply trying to solve a system of equations and mathematica can't do it for all values over the region of interest. I have a 3x3 matrix that has a specific parametrization and after squaring the ...
2answers
97 views

### NSolve won't act on very large powers

I noticed that NSolve isn't running properly when I have some seemingly harmless numbers in my expression. Here is a simple example: ...
2answers
72 views

### FindInstance function

I have a question concerning the FindInstance function. If I write FindInstance[c == 3, {c, l}] I obtain {{c -> 3, l -> 33/10 + (8 I)/5}} Is there any ...
1answer
141 views

### Verifying the outputs of 'Solve'

I got a solution for the equation ...
1answer
225 views

### NDEigensystem cannot solve numerically the 3D Coulomb problem, while DSolve returns the right answer

After having derived by hand the eigenvalues and eigenfunctions for the 3D and 2D hydrogen atom, I want to solve the systems numerically using Mathematica. I need to do this because my next step is to ...
1answer
42 views

### Solve returns empty list on system of 62 linear equations with undeclared known variables

Context: I am trying to solve a set of equations generated by hand from a complicated, but not particularly strange system via Newton's Second and Third Laws, and a few constraints. All the resulting ...
3answers
211 views

1answer
91 views

### Solve the interpolating function

I would have asked how to obtain the x given the y in an interpolating function, and I found the answer from here. But another question raised. I was dealing with measurement of the spectral ...
2answers
41 views

### how do I find the unknown coefficients of coupled equations

How do I find the unknown constants $x, y, z$ interms of a and b, using Mathematica. \begin{split} 1&=-x+y+z \\ 0&=y\frac{-4a}{b-\sqrt{b^2+8a^2}}+z\frac{-4a}{b+\sqrt{b^2+8a^2}...
1answer
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1answer
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### Expanding in terms of a function in Solve

I am almost sure Mathematica has a way to do what I am looking for. I am trying to fit a quadratic T(x) = ax^2 + bx + c to three values of the function analytically. I proceed as follows: ...
2answers
58 views

### Using result of Solve as plot parameter [closed]

Recently I have faced a problem I would appreciate it, if you helped me I have the following code in Mathematica I want to plot a function let say z * 10 * t where <...
1answer
68 views

### Solve equation in a interval

I have a particle bouncing in a rigid box, my code is this: ...
2answers
110 views

### Solve implicit system of equations

Hello everybody I try to solve this system of functions and try to plot it: x == 0.5(1.+Tanh[0.5*(x*y^2-eps1)/t] y == Tanh[(x^2*y+eps2)/t] with eps1 = 0. and ...
0answers
43 views

### Impose conditions on differential equations

This is my first post in Mathematica Stack Exchange, so thanks for your help and sorry for any rookie mistakes. I am solving the Einstein equations for two vectorial pertubations h_Alpha and v_Alpha ...
1answer
40 views

### “MemoryAllocationFailure” in DSolve

Mathematica 10.4, Windows 10, 6 GB RAM, 64 bits When I trying to solve DSolve[{v'[t] == 100 - 0.15 v[t]^2, v[0] == 30}, v[t], t] I get ...
3answers
212 views

### Solving equation

How can I solve this equation: ((a^2 - 1)*((a^2 - 1)*ArcTanh[a] - a))/(2*Sqrt[2*(a^2 - 1)^4]) == C*x I am looking a solution for $a$ in function of $x$. I tried <...
1answer
106 views

### Maximize a variable in NSolve Function

I want to solve a set of trigometric coupled equations with the NSolve funcion while at the same time trying to maximize a variable which has to be real and between ...
3answers
183 views

### Cantor Pairing Function

I'm inspecting the Cantor pairing function, that we can find on this link here. But the strange thing is that Mathematica is outputting a wrong result to me. The code below shows the strange behavior....
0answers
39 views

### Using previous outputs and equations for 3d plots

I am extremely new to Mathematica, and am trying to obtain some plots for my research work. I need to find the roots of a polynomial, and using the roots individually, I need to obtain another ...