# 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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33 views

### Evaluate with numbers from list

This code works: x=2 y/.Solve[y==x^2] Out= 2 Out= {4} So above I put number in variable x and getting the result of ...
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### Underdetermined system of equations

Could anyone help me solve this probably simple equation? ...
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### Ploting output of Solve[] and Expand[] that returns two results on one plot with Plot[] [closed]

I have code: Expand[Solve[x^2 + y^2 == 25, y]] output is: For this code: y /. Expand[Solve[x^2 + y^2 == 25, y]] output is: ...
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### Is it possible to get a symbolic or numeric relation when solving a transcendental equation? [closed]

Here is the code. Solve[(1 - E^x + (3 x^2)/2)/(2 x) == a, x, Reals] Unfortunately, Mathematica told me that this system cannot be solved with the methods ...
83 views

### How can I solve $\coth (2 x )=x$? [duplicate]

I have this equation $$\coth (2 x )=x$$ and I want to solve it to find $x$. The methods Solve and Reduce do not work. Coth[2 x] == x
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### what does that mean?? How to fix it? [closed]

Hey I need help to fix this problem please I am looking to solve form factor of scattering ...
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### How to solve system of PDE's with complicated initial and boundary conditions

I am trying to solve the Cavity problem given in Paper by Mansour et al. with a physical model . System of PDE and B.C are . How can I impose boundary conditions like this? Code ...
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### Find the condition under which an inequality holds

I've got an inequality of 8 non-negative parameters (arising from a 5x5 matrix) and would like to find a condition under which my inequality holds. The condition would be an inequality too of these ...
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### How to deal with unknown variables in NSolve?

I am trying to solve these equations by using NSolve and want to plot $p1^{2}+p2^{2}$ v/s P0. But there is some problem, it is showing running... but not showing any error. I don't know where I am ...
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### Why mathematica does not solve the equation $x\left \lfloor x \right \rfloor=10$ for $x$?

The equation $x\left \lfloor x \right \rfloor=10$ has a real solution, which is $x=\frac{10}{3}$. But when I type Solve[x*Floor[x] == 10, x] a message comes: "...
138 views

### Verify an inequality of many parameters

I've got an inequality of 10 non-negative parameters (arising from a 5x5 matrix) and would like to verify whether it holds. I tried the following, which doesn't seem to work: ...
38 views

### how to solve a quadratic diophanic equation on integers and obtain various results

This quadratic di equation has more results, as it came to them. I can only think of this FindInstance[(4 p + 3 q - 2) (p - 1) == (6 p + 2 q) q, {p, q}, Integers] ...
52 views

### Using Reduce with a Interpolation function

I am trying to find all the solutions of an equation that contains an interpolation function int, where int=Interpolation[data] (...
86 views

### fixed rate mortgage

I am trying to make sense of how mortgage repayment figures are calculated for two tier mortgages, where you fix your interest rate for a certain period and after that period, you fall back to the SVR ...
126 views

### Simplifying the final coefficient expression of the solution to a Laplacian

I have been trying to solve a boundary value problem analytically which involves a three-dimensional temperature Laplacian over a parallelepiped. In the final step of my solution, using the two non-...
27 views

### why mathematica Holds the Solve on the set of equations in the diagonal a matrix?

Say I have a simple function F[x_, y_, z_, r_, a_, b_, c_, d_] := (1 - a + b - (b/3) (c x + d (y + z + r))) x And I want to solve the set of equations given by: <...
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### Find non-unique Hermitian solution to pair of matrix equations

This is a continuation of my previous question here, but I previously did not fully specify some of the restrictions on the matrices and so the solutions posted there were not that helpful. I'm ...
52 views

### How to get the result from a RootSum?

While working on an integral, I got this scary-looking expression. I tried to use // Normal // ToRadicals // FullSimplify to get the answer, but it is taking lot of ...
2k views

### periodic boundary conditions and NDEigensystem

Mathematica 10 has a splendid new function, NDEigensystem, that makes it possible to solve Sturm-Liouville problems numerically in a single step. I have not however been able to find a way to get it ...
128 views

### Make Arrows Smaller

I have the following program that describes a 3D curve in space with an osculating circle and TNB vectors moving with the curve. The arrows indicating the TNB vectors are way too large making it seem ...
30 views

### Get Solution range of NSolve

I have a numerical solution and when I solve it with NSolve, and substitue the results in an expression, I get something like: 1 + x + x^2 if 0 < x< 10 I ...
73 views

### Solving Inequalities using Mathematica

How can I solve this inequality using Mathematica? Sqrt[B^2 + J^2] Cosh[(2 J)/T ] < J Sinh[ (2 Sqrt[B^2 + J^2])/T] where T, J, and B are reals and they are >...
63 views

### How to solve these complex equations for plot?

I am trying to Plot this code but it is not showing any plot. I want a bistable type plot between "NL" and "P0" and there are six equations and six unknowns. The code is given ...
51 views

### Problem of Encountered non-numerical value for a derivative at t == 0

I try to solve this equation numerically : eq= z''[t] + (2691+ D[Log[Abs[z'[t]^2]],t]) (z'[t]^2 + Abs[z'[t]]^2 ) == 0; By ...
77 views

### Converting an equation to the form $ax+by=c$

I have a linear equation that comes as a result of applying orthogonality on a non-homogeneous boundary condition with two unknowns $C_1$ and $C_2$. Can someone help me to express this equation in the ...
103 views

### Solving symbolic system of non-linear equations takes too long

I am trying to solve a set of system of symbolic non-linear equations: ...
83 views

### correct use of the command FindInstance

I have tried to solve this system for numbers that go from 1 to 10 non-repeated integers, this occurs to me ...
449 views

### Numerical solution to a nonlinear Ordinary Differential Equation

I am trying to solve the following ODE for $f(x)$: $$x f' - f = \frac{(f')^2}{\gamma^2}[1-({f}')^\gamma]^2$$ where $\gamma < 0$ and real, which makes the ODE highly nonlinear. Since I am not ...
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### How to chop complex number from solution solve using a model

Hi I have a set of 4 solution that was solved using a 4th order polynomial equation. I have noticed that some of the real number solution occurred through the list of 4 set of solutions. I have ...
913 views

### Using RSolve correctly

I am having problems persuading Mathematica to solve even the simplest recurrence relations. As an example, how would you do the following? ...
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### Problem solving a function using FindRoot and then plotting it

When I run the following code: ...
647 views

### Plotting the solution of a Chini differential equation

In DIFFERENTIAL EQUATION SOLVING WITH DSOLVE by D. Kapadia, there is a Chini differential equation : sol = DSolve[x'[t] == 5 x[t]^4 + 3 x[t]^(-4/3), x[t], t] ...
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### How to solve complex equations and plot the graph?

I am trying to solve these equations and want to plot the value of $a^{\dagger}a$ versus P0. I have tried this code but this gives me an error like "Conjunction::argr: Conjunction called with 1 ...
41 views

### How to solve integral of second-degree exponential function?

I am trying to solve the internal of the second-degree exponential function. But Solve fails to give the solution. Is there any way to get the solution? By the way, I don't understand the ability ...
110 views

Is there a general way of re-writing a function of two variables as a product of two functions, $$f(x, y) = g(x)h(y)$$ Specifically, I’m trying to write an expression, $$f(x, y) = \frac{a y - x}{y - 1}... 1answer 90 views ### Solving a system of polynomial equations - can I be sure that the number of solutions, and the solutions are correct? I need to solve a system of two polynomials with integer coefficients in two variables, \{Q_1(w,z)=0,\,Q_2(w,z)=0\}, and want to compute all real solutions. I'm able to run ... 1answer 98 views ### Solve 2D Difference Equations If I have a system of difference equations$$ \begin{cases} x(n + 1) = x(n) + x(n) y(n) + y(n)^2 \\ y(n + 1) = y(n) - x(n)^2 + y(n)^2 \end{cases}, \text{ with } \begin{cases} x(0) = 1\\ y(0) = 2 \end{...
How can I find $f(x)$ in the interval $(x_1,x_2)$? I know the values of the coefficients as $c=0.5$, $b=1.1$ and $(x_1,x_2)=(-10,10)$. f[x] == c Cos[2 f[x]] + b x ...