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

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0
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0answers
8 views

Solve Equations show no answer

I want to solve these equations but mathematica show no answer ...
0
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1answer
31 views

finding the coordinates of intersection point of two complicated implicit function

I have two complicated functions and i plot the contours of them like this: ContourPlot[{f[x,y]==0,g[x,y]==0},{x,x1,x2},{y,y1,y2}] I would like to find ...
0
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0answers
62 views

Gauss-Jordan program in Mathematica

Hi to everyone I made this program to solve a linear system by Gauss Jordan, this is my code to solve the system: ...
0
votes
1answer
55 views

Nested double sum does not converge

I am quite a beginner, and have the following problem. I have a sum that comes from Poisson distribution and for each index there corresponds a binomial-type sum. I try to find its root for the ...
3
votes
1answer
47 views

Solving biharmonic equation with Mathematica

I would like to solve a biharmonic equation in polar coordinates of the form: $\Delta \Delta \Phi[r,\theta] = r^i cos(j \, \theta) \quad i,j \, \epsilon \, \mathbb{N}_0 $ I know that a solution for ...
0
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0answers
46 views

Solving a non-linear equation [duplicate]

I have one non linear equation, and I am trying to get value of x but when i employ Solve function as below ...
0
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1answer
45 views

System of two implicit equations subject to (complicated) constraints. Infinite recursion?

I am trying to solve a system of two equations subject to 3 constraints which are rather implicit. With my (naive) code I obtain a list of recursions that Mathematica keeps on writing until I abort ...
0
votes
3answers
78 views

Issue finding roots in a polynomial [on hold]

I am trying to find the roots of the polynomial (-2 + x)^3 (-2 + x^2) (-4 + x^3) (4 + 2 x^2 + x^4) (-8 - 8 x - 2 x^2 + x^3 + x^4) . I am using the command ...
2
votes
2answers
272 views

How to solve an equation with a nested function

I have the equation f[f[x]] == 28 + 9 x How can I solve this for f[x]? I note that this post relates to the topic, but ...
1
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0answers
56 views

Solving an equation entered by the user via the Input function

I am new to Mathematica. I am trying to create a program that takes in an equation from user input and then gives the answer. I started with a manipulate function as I created a similar program for ...
0
votes
0answers
32 views

Change of Basis Set of Equations [on hold]

Given a set of equations in ${x,y}$, e.g. $$x(a-2b) = y(b+c)$$ $$x(b+c) = y(b-c)$$ $$x(b+c) = y(a-2b)$$ is there a way to rearrange the equations such that they are now expressed in terms of $f=x+y, ...
2
votes
2answers
50 views

Plotting the results from Solve in a Manipulate expression

I am a self-taught Mathematica user, trying to make some progress. This is my code: ...
1
vote
2answers
87 views

Find smallest solution in Solve's solution set

When an equation has multiple solutions, how do you find the first solution? Example: Say we're trying to find the first positive x-intercept of the cosine function: $cos(x)=0 \land x \ge 0$ ...
1
vote
2answers
69 views

Error In polynomial Root Finding

I have a polynomial in y like so: 2.00855*10^20 + 6.89796*10^20 x y + (5.17347*10^20 + 5.92241*10^20 x^2) y^2 - 1.4806*10^21 x y^3 + 7.77316*10^20 y^4 == 0 I ...
0
votes
2answers
143 views

Solving equation containing ArcTan terms

IN MY EDIT I DESCRIBE HOW I GOT TO THAT EXPRESSION AND THE ORIGINAL PROBLEM. I have this expression: ...
0
votes
0answers
56 views

Solve equations involving summation expressions in Mathematica

I am trying to solve the simple linear regression equation analytically in Mathematica (not using builtin functions). I managed to calculate the gradient as follows f is loss function using RSS and ...
0
votes
1answer
59 views

Why is FindRoot failing to evaluate this function? [closed]

I have a (somewhat long) script which runs cleanly until the very last stage. Here, I'm using FindRoot to attempt to parameterize implicit curves in the zero set ...
1
vote
0answers
53 views

Numerically parameterize portion of $F[x,y]==0$

I have a relatively complicated function of two variables F[x,y] whose zero locus contains a number of intersecting paths in the $x,y$-plane. A problem I've been ...
1
vote
1answer
61 views

Automation of Perturbation Solution

I'm trying to solve an equation of the form $$ R(\theta)f(\theta)+hg(\theta) = 0 $$ for small $h$, where $R$, $f$, and $g$ are functions. I've assumed a power series expansion for $\theta$ in terms ...
3
votes
1answer
246 views

Reduce a complex inequality

Reduce[Abs[1/(1 + I/Sqrt[α])] < 0.5, {α}] It is taking long time to run. Can any one help me to get the reduced condition in terms of $\alpha$ or its modulus. ...
1
vote
2answers
72 views

Using solve on conditional functions

I know that the code is pretty long, but most of it is just defintion. Do you see why the Solve gives me "his system cannot be solved with the methods available to Solve" back? ...
3
votes
1answer
157 views

How can I combine NDSolve[] with NSolve[]

Consider the two below ODEs with following dependent B.C. In the boundary conditions $k$ is an unknown. $$y_1''(x)=x$$ $$y_2''(y)=0$$ $$y_1(1)=y_2(1)$$ $$y_1(-k)=y_2(-k)$$ $$\frac{\text{dy}_1(1)}{\...
1
vote
1answer
59 views

Matrix equations solving

can you explain me the easiest way for solving this matrix equation? I have this matrix: a={{-4,1,3,0},{-2,7,1,-1},{1,-1,9,-3},{-1,0,5,-10} and the Equation is: ...
3
votes
1answer
79 views

Precision of FindRoot

Consider the following code: ...
0
votes
0answers
66 views

Avoiding divide by zero to simplify an expression enough to solve

I have a very complicated expression that I'm trying to set to zero and solve. I simplify by substituting in variables, but Mathematica isn't fully simplifying it -- my guess is because it thinks it ...
1
vote
1answer
72 views
0
votes
0answers
62 views

Why can't Mathematica solve this complex equation?

So I want to find the complex part of Rthev,equate it to zero and solve for ω but it won't let me. Is it because it thinks ...
0
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0answers
71 views

How do I solve 14 simultaneous equations? [on hold]

So I have trouble solving these 14 system of equations. It worked fine analytically for 6 equations but I applied this for 14 and it doesn't seem to work because of the large computation time. I don't ...
1
vote
1answer
78 views

How can I solve a set of equations with variables and eliminate a few variables at the same time?

I just started learning Mathematica since I needed for my current research. I'm trying to solve a set of equations with different variables, eliminate a few variables in the set, and express one ...
1
vote
2answers
79 views

Determining the value at which a function becomes non-real or undefined

If I have a function $f(x)$ that I only know numerically and that returns a real value for some range of values $-\infty < x \leq a$ and complex values for $a < x < \infty$, how can I ...
1
vote
1answer
43 views

Solve matrix equation for matrix

Is there any function like Solve but designed to deal with matrix equations? Something like: ...
1
vote
1answer
103 views

Evaluate an integral with parameters

I already asked this on stack overflow but was redirected here. I am trying to solve the (highly non-linear) following system of equations : with and $g_0$, $\Lambda$ are positive constants ...
0
votes
0answers
37 views

What is the default method used by NSolve

I have a system of 6 polynomial equations of the form aijk xi xj + bik xi = ck (k=1,2,...,6; summation convention on i & j) I am using NSolve[{eq1,eq2,...,eq6},{x1,x2,...,x6},Reals] What ...
2
votes
2answers
70 views

solve system including piecewise function

I've read posts about how to do this in a direct way, but the method doesn't work for my simple system? -- see code: ...
-1
votes
0answers
30 views

Finding roots to Interpolation function [duplicate]

I am attempting to find the roots (intersection is constant Y-value) of an Interpolation function. I can do this by observing the plot and then entering search start values based on the visual ...
0
votes
1answer
55 views

function definition, $ symbol apparition after variables [closed]

I have a proble with a system of two differential equations ...
0
votes
2answers
36 views

How to solve equations involving binomial and summation expressions

Mathematica is taking forever to solve the following equation. Is there any other way t solve this equation for x? ...
1
vote
1answer
40 views

Determine parameter from which on there is no more root for a given function

Let $\gamma>0$ be a real number and $\Phi(r)=\frac{1}{r}-\frac{\pi}{4}\left(H_0(r/2)-Y_0(r/2)\right)$ defined on $[0,\infty)$, where $H_0$ is the Struve function of order zero and $Y_0$ is the ...
2
votes
1answer
82 views

Way to simplify an inequality with many variables

my problem is the following: I have three inequalities in five variables $x,u,a,b,c\in \mathbb{R},x>0 $: ...
0
votes
1answer
64 views

Do not understand the result I'm getting from Solve [closed]

I did Solve[k2 Cos[x] - k1 Sin[x] == 0,x] Since tangent is sin over cos, the solution must be arctan(k2/k1) But ...
1
vote
1answer
48 views

How to solve an iterative integral equation for a function in Mathematica 8.0?

I would like to solve the following iterative integral equation in order to find the functional form of $P_{0}(k)$ numerically and then use it subsequently for the rest of my code: ...
1
vote
0answers
42 views

diophantine linear equation with condition on the sum of coefficients

I am trying to solve the following diophantine equation x*a + y*b == c where a,b,c are integers and the absolute value of their sums is, for instance, 4. Then I ...
0
votes
1answer
30 views

FindRoot outputs a lot of nlum and ReplaceAll errors before outputting (close) root

I'm trying to find the root of the root function when some other variable is subtracted. I.e. FindRoot[root[theta, r, h]-H, theta] Whenever I do this, FindRoot ...
0
votes
1answer
43 views

Evaluating Root forms in a Table [closed]

When I put a Root form in table, the parameters of the Root form don't evaluate. I don't know how I can indexed values substituted into root form in the table to get have numeric output. ...
1
vote
2answers
135 views

Solving system of equations with (nested) Bessel Functions

I'm trying to find solutions to a system of equations which include Bessel functions. It feels like the problem for mathematica is that the arguments of the Bessel functions are functions themselves ...
1
vote
1answer
68 views

Nonlinear Markov chain (numerical simulation)

Suppose you have a linear Markov process, and you can write it as x(t+1) = Ax(t). Here x is the vector of values, and A is the transition matrix. Since this is linear, it can be solved analytically, ...
2
votes
1answer
126 views

Undershoot/Overshoot Method for this differential equation?

I have tried to solve this equation for some weeks and I am not capable. I have read in articles that it is easy with an undershoot/overshoot method, but I don't know how to do it. $y''+\frac{3}{x}y'-...