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

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3
votes
1answer
109 views

Inaccurate answer for a system of equations

When I solve the following system of 6 equations by NSolve, it gives me an answer set; however this answer won't make the 2nd equation equal to zero (i.e. when I put the answers into ...
-1
votes
1answer
82 views

Find a minimum value which satisfies an equation

I have to find a minimum value of "a" which makes x=-a+b+c, y=-a+b+c^2 positive where a>1, 0 ...
4
votes
3answers
194 views

How do I generate a set of n-tuples containing integral solutions to a linear equation provided certain constraints?

Let $m,k,p$ be fixed positive integers. I want to create a table of k-tuples $(x_1,x_2,\ldots,x_k)$ comprised of solutions in positive integers to the equation below: ...
3
votes
4answers
233 views

How to merge permutations obtained from Solve on multiple variables?

When I compute the following expression to find integer solutions of the equation (x^2 + y^2 + z^2 == 14^2) ...
9
votes
3answers
195 views

How to find the solutions to $a+b+c+d=60$?

How can I find all the solutions to: $$a+b+c+d=60\quad (0\leq a,b,c,d\leq 30,\; a,b,c,d\in\mathbb N)$$ I've tried to use Solve[], but it says that there are more ...
6
votes
1answer
249 views

Solving $\frac{dx}{dt} = A \frac{ (1-x)}{(t-t^2)} - \frac{(B*x -C*x^2)}{(t-t^2 )*(t-x)}$

I would like to solve the following equation: $\frac{dx}{dt} = A \frac{ (1-x)}{(t-t^2)} - \frac{(B*x -C*x^2)}{(t-t^2 )*(t-x)}$ I have already posted it here, but still it doesn't work for me (I ...
0
votes
2answers
100 views

Solving two variable using two expressions each involving summation

I am trying to solve for h1 and h2 using function solve as in below code, Expression in solve has two equation each equates sum ...
0
votes
1answer
73 views

Complex Polynomial roots [closed]

I have the polynomial $p(z)=1-z^3$, I am using mathematica to get all three roots of $p$, say $a, b$ and $c$, obviously $$ 1-z^3=(z-a)(z-b)(z-c) $$ However, mathematica gives a wrong answer by saying ...
0
votes
2answers
71 views

Getting the first solution instance

How do I get Mathematica to stop a solver and give a result as soon as it finds the first solution instance? I tried this: ...
0
votes
1answer
64 views
0
votes
0answers
53 views

Sharp Ratio Maximization, Closed Forms

I am trying to get a closed form for the following first order conditions (n=4): Here's the nb-File. The code is as follows: ...
6
votes
1answer
124 views

Closed form of two-layer recurrence

I am trying to find a closed-form expression for $A(0)$, described by the following recurrence forms, as a function of $L$ and $d$: \begin{align} A(\ell) &= 1 + 2^d A(\ell+1) + \sum_{g=0}^{d-1} ...
0
votes
1answer
56 views

Trouble in finding instances of values of variables that satisfy an inequality

Consider the following mathematical expression with complex numbers (phasor) and two variables (lambda and ia2): ...
6
votes
2answers
323 views

Solving a two variable two equation trig expression

I am trying to use Solve to get what two angles (A and B) are in a problem I have. ...
0
votes
1answer
150 views

Plotting level curves for 2-variable exponential equation (Lotka-Volterra) - how?

I have $$\frac{e^{(d x + b y)}}{x^c y^a}$$ Incidentally, this is the energy integral for Lotka-Volterra as given by my lecturer's notes. I would like to draw the level curves for this equation for ...
1
vote
0answers
74 views

How much time for solving a system of equations?

I wrote the following code for system of 11 equations; however when I run, it shows "Running" and has not converged to any answer after 2 hours. Please let me know whether it is normal or how I should ...
0
votes
1answer
79 views

Problem in solving non linear set of equation?

I am trying to solve a set of non linear equation but using the function nsolve but mathematica is not giving me proper answer. The code is given below. ...
0
votes
2answers
180 views

Exporting and Importing solution sets from NSolve

I have a rather large data set that I need to solve for, then save to my hard disk and import in the same format at a later time. This proves to be tricky. I use ...
1
vote
1answer
95 views

Solve for a variable using expression involving sum of quantities

I am trying to solve for h1 using function solve as in below code, Expression in solve equates sum of two expression. Both left hand and right hand side of expression is the sum of four quantities ...
3
votes
0answers
120 views

Stability analysis of transcendental equation (stability crossing curves)

I am working with a non-linear delay system with three scalar delays. After taking the Laplace transform of the linearized system, the characteristic function is a transcendental equation with three ...
0
votes
0answers
38 views

How to solve a system of equations which includes vectors? [duplicate]

I'm starting to wonder if this is something that mathematica just can't do? I thought something like this might work: ...
1
vote
1answer
64 views

Reducing a system of vector equations

I'm trying to solve a system of vector equations. I know this is solvable since I've done it myself by hand (I reduced it to solving the root of a quartic anyway). I'm trying to do it in Mathematica ...
3
votes
1answer
663 views

HarmonicNumber problem

I am looking for all the roots of HarmonicNumber, in the domain [-30, 1] and [0, 6000] for the real and imaginary parts, respectively, and where the parameter ...
17
votes
1answer
1k views

Is Mathematica `ContourPlot` function really so efficient?

I wanted to find the roots of the function $f(x,y)=\sin(3.2x)\sin(1.3y)-2.1 \sin(1.3x)\sin(3.2y)$. This is what the function looks like: ...
2
votes
1answer
199 views

NDSolve doesn't work for this simple differential equations

I try to use NDSolve to do this partial differential equations, but the result is wrong... The source term is a Gaussian pulse as time and an exponential decay with the depth z. The result should be ...
0
votes
1answer
43 views

Defining a function in terms of a solution returned by Solve

The title is a little ambiguous, but I didn't know how else to put it. What I'm trying to do is solve a system of equations ...
0
votes
1answer
90 views

Use FindRoot to get the root with minimum imaginary part

For example, define test[z_] := Cosh[0.5132928614530164 z] + 0.5934823341977118 Sinh[0.5132928614530164 z] And ...
0
votes
1answer
65 views

List manipulation performance or how to make independent list copy

I have a task to solve some system of equations with NSolve and print graph of it, depends on parameters. Something like this (maybe it is not a good example and does not always have a solution, but ...
0
votes
1answer
105 views

Solve ${\rm BinomialDistribution}(x;\,n_1,\,p_1) = {\rm BinomialDistribution}(a-x;\,n_2,\,p_2)$ in terms of $x$ [closed]

I'm totally a novice with Wolfram software, so please forgive me if the question is nonsense. I want to solve the following equation in terms of $x$: $\quad \quad {\rm ...
1
vote
1answer
427 views

Marking the points of x-intercept on a plot

OK, I have a nice plot of some oscillating motion. I can read some stuff off the graph, but I thought it would be cool to show a dot where the curve hits the x-axis and a little label showing the ...
1
vote
2answers
83 views

Substituting solution into the equation

I need to solve 6*6 equations over and over and put the coefficient into the equations again. But I don not know how? Can anyone help me? ...
3
votes
3answers
2k views

Implementing Newton's method

I have this question on coding Newton's method in Mathematica. I have some code to go by but I have no clue if it's computing the functions in the right order. The book is the numerical methods ...
4
votes
1answer
171 views

How to solve a conditional inequality?

I am trying to use Mathematica to solve a conditional inequality. Find all (real) numbers $a$ and $b$ such that $|a| + |b| \ge 2/ \sqrt{3}$ and for any real $x$ the inequality $ |a\sin x + b \sin ...
0
votes
1answer
159 views

Manipulate Solve

I have seen similar questions and answers but it did not help me. I would like to see effects of three constants in equations resulted from solve command. conditions are ...
1
vote
0answers
152 views

How can I improve the solution of my PDE?

I want to improve the last code to find a better solution for umi. For now I'm using only MaxStepFraction. Also, when I put no ...
1
vote
3answers
192 views

NSolve returning an empty set

Dear Mathematica experts. I am a chemist looking to use Mathematica to solve a system of equilibrium equations. I have a system of 8 polynomial (I think) equations with 8 unknowns, yet when I use ...
3
votes
3answers
185 views

When NSolve fails due to a differential situation?

c = 1.1111; y[x_] = x - c Sin[x] NSolve[y[x] == 0, x] The method has procured no result. Successive derivatives were plotted in an attempt to fix the problem. ...
3
votes
3answers
619 views

Finding intersections of two parametric curves

I am dealing with the root finding of two parametric data curves (data below). I have already checked Parametric Interpolation of 2D data, which I found useful for plotting, though it is not adequate ...
0
votes
1answer
118 views

Solve seems broken after I installed the package Tomatlab.m

After I downloaded the Mathematica package ToMatlab.m, Solve does not work as before: ...
3
votes
3answers
315 views
0
votes
0answers
58 views

NSolve running for ever

I have troubles running NSolve for my physics problem. I am new to Mathematica, which is why I might be missing some key solutions. I have the following function with the variables: ...
1
vote
0answers
88 views

Solution Branch Switching of Quartic

Im using a closed form solution for quartic equation. In the quartic equation, there are parameters that are being varied and therefore the solution changes depending on these parameters. The ...
3
votes
0answers
265 views

Nonlinear FEM and FindRoot

I'm trying to develop a kind of nonlinear FEM application using mathematica to solve a bvp like the following: $$ \gamma(u') ~u^{iv} + 2 \gamma'(u') u''' u''+ u''^3 = f(x) $$ where $u = ...
0
votes
2answers
54 views

Selecting the maximum value from the results returned by NSolve

I'm trying to select the maximum value from the answers Mathematica 7.0 is getting from a simple basic NSolve algebric equation : ...
0
votes
1answer
97 views

A question about calculus and Programming

I am a very new user and I would like to know how to calculate the following operations in Mathematica. Honestly this is not a homework. I am an french architect and I would like to be back in Math ...
0
votes
1answer
59 views

using FindRoot to solve 3 simultaneous equations [closed]

I'm trying to solve 3 simultaneous equations derived from an electrical circuit of a common source amplifier. ...
-2
votes
1answer
77 views

Sign of a symbolic expression as a function of parameter values

I need to know the sign of the following expression for p[t] = z/(1-a), as a function of the parameters {a, b, c, z}: ...
1
vote
1answer
141 views

Hill function (equation) vs a gene

So im trying to make one equation equal another to solve for all physically realistic values of $X$. Hill function is: $$ F(X)=\frac{1}{1+(\frac{X}{K})^n} $$ and Gene Z equation is: $$ Z(X) = ...
0
votes
0answers
62 views

NSolve can not handle a PolyGamma equation

I would like to solve the following equations numerically: ...
1
vote
1answer
82 views

Trying to find solution for system of ordinary differential Equations [closed]

I've got 2 functions: A'[t] = (0.5/(1 + (B/k1)^n)) - 0.2*A B'[t] = (1/(1 + (A/k2)^n)) - 2*B with conditions of ...