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

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1
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1answer
81 views

DSolve - Complex Number Solutions

some of you know that I have been working on my dissertation of Game-Theoretic Modelling of Cybersecurity (Thank you again to everyone who has helped me with Mathematica so far). The differential ...
2
votes
1answer
82 views

Can't obtain Real results using NSolve

I am trying to find the critical properties of the Carnahan-Starling equation of state, $$p=\rho R T\frac{1+b\rho /4+(b\rho/4)^2-(b\rho/4)^3}{(1-b\rho /4)^3}-a\rho^2$$ using this system of equations, ...
2
votes
1answer
99 views

Product of $N\ 2 \times 2$ matrices and subsequently solving an equation dependent on the product

I have $N\ 2 \times 2$ matrices, each one containing one variable energy which may be complex. I want to muliply them all together to a single matrix ...
0
votes
1answer
62 views

Solve system of equations using a “singular” condition [closed]

I want to find a vector $x$ that is orthogonal to some vector $u$. The vector must satisfy the conditions $u\dot x = 0$ and $|x|^2=1$. Then I pass to Mathematica the next code: ...
1
vote
1answer
46 views

Finding root when using Apply command

I have normally two equations system which I reduce to one equation and make its graphic. I could make the graph of the reduced equation but I can not find the appropriate command to find its root. ...
0
votes
1answer
106 views

Solve this equation explicitly for $\beta$

Solve this equation explicitly for $\beta$: $$T_{12}=\frac{x_{11}+x_{22}}{1+|\beta|^2}\beta$$ $x_{11}$ and $x_{22}$ are positive real numbers where $x_{11}>x_{22}$ and $T_{12}$ and $\beta$ are ...
-1
votes
3answers
64 views

Calculate an expression given constraints [closed]

How can I solve the following problem using Mathematica? If $a+b+c=0$ and $a^2 + b^2 +c^2 = 0$, calculate $a\,b+b\,c+c\,a$.
0
votes
0answers
56 views

DSolve DAE echoing - no solution/response

I am aware that there are lots of questions about this topic but they are all slightly different. I am attempting to program a cybersecurity infection model and there are 4 states that a computer can ...
3
votes
1answer
70 views

SolveAlways 'never' completes

After allowing Mathematica to run on ...
2
votes
1answer
78 views

Mathematica's Solve[] and LinearSolve[] doesn't work to solve a system of equations IF parameters are not replaced

(I'm working on Mathematica 10.3) I have a system of 81 algebraic linear equations with 81 variables (variables are a1 to a81). ...
5
votes
1answer
184 views

$x^6-2\varphi^5x^5+2\varphi x+\varphi^6=0$ solving in radicals

How to solve the equation $x^6-2\varphi^5x^5+2\varphi x+\varphi^6=0$ in radicals using Mathematica? where $\varphi$ is the golden ratio. Solution is Ramanujan's Class Invariant $G_{125}$, Class ...
3
votes
1answer
104 views

Proof or find counterexample to inequality (in three vars)

I'm trying to show \begin{eqnarray*} \left(\frac{1-q^r}{1-q^n}\right)^{\frac{1}{n-r}} \left(\frac{q^n \log (q)}{\left(1-q^n\right) (n-r)}-\frac{\log \left(\frac{1-q^r}{1-q^n}\right)}{(n-r)^2}\right)&...
2
votes
1answer
89 views

Inputs which make two function have the same value [closed]

Suppose I have two function f(x1,...,xN) and g(x1,...,xN). How can I find the values ...
0
votes
0answers
89 views

solving an equation containing an complex integral

I want to solve a numerical equation which include an integral. The problem parameters are : w (is a complex : w = wr +I wi), <...
0
votes
1answer
123 views

Given $y$, find the $x$ value of a point on a Bezier curve

I have linear equation of Bezier curve with one control point: f[x_] := (1 – t)^2 x0 + 2 (1 – t) t x1 + t^2 x2; f[y_] := (1 – t)^2 y0 + 2 (1 – t) t y1 + t^2 y2; ...
5
votes
0answers
159 views

VERY slow to solve a nonlinear equation involving matrix eigenvalues

I am trying to solve a problem similar to the following: ...
-1
votes
1answer
94 views

Parametric solving a nonlinear equation and plotting answer [closed]

I want to get x and y as a function of z in below nonlinear equations and plot ...
3
votes
1answer
112 views

plotting a function on a (x,y) plane

I looked at different questions asked concerning the error message that I get but it did not help. I try to plot a function. Here is the code that I use ; ...
9
votes
3answers
293 views

Labeling solutions of an Eigenvalue equation involving Bessel functions

I'm solving the Schrödinger equation for a particle in an annular geometry with hard wall boundary conditions and I've reduced it to the following equation: $$J_m(k\,R_1)\,Y_m(k\,R_2) - J_m(k\,R_2)\,...
1
vote
0answers
87 views

Truncate an infinite continued fraction at order 2000

I want to solve an equation which contains an infinite continued fraction F(n). Then I must (obviously) truncate this continued fraction at n=2000. The problem here is tha Mathematica does not ...
0
votes
0answers
98 views

Solving system of Fredholm integral equations of the second kind

How can we generalize the code previously introduced to solve the Fredholm equation of the second kind to the case of a system of Fredholm integral equations of the second kind? $$ f_{1}(x)-\lambda_{...
3
votes
6answers
305 views

Avoiding a For-loop when finding the solution to a set of polynomial equations

There are several examples and questions regarding Map, but I couldn't find what I need. This is a minimal working example. I have two functions $\qquad f=x^4+y^...
3
votes
4answers
512 views

NSolve didn't get the answer for my equations within 24 hours

I have two polynomials as function of $wa$ and $wb$ , I am going to show those polynomials. This is the expression for $GS65$: ...
1
vote
1answer
99 views

Solving a system of non-linear equations?

I want to solve the following system of equations: ...
3
votes
1answer
94 views

Dsolve and Differential Equation for botnet defence

I am currently using Mathematica to solve $\frac{\mathrm{d}x(t) }{\mathrm{d} t} = cv_{H} (1-x) + \beta x(1-x) - (\gamma_{min} - v_{D}(\gamma_{max} - \gamma_{min}))x$ with $ x(0) = 0$. In the ...
10
votes
3answers
395 views

Bug: Wrong results from NSolve on coupled polynomials. WorkingPrecision->Automatic fails

OP UPDATE: I received an email from WR on 1-18-2016: "...It does appear that the NSolve function is not behaving properly in this case and I have forwarded an incident report to our developers with ...
3
votes
1answer
115 views

How to solve coupled multi-variable polynomials?

The following code generates two polynomials $q_1$ and $q_2$ in complex variables p and c: ...
3
votes
1answer
84 views

Solving a list of equation which takes so much time

I try to solve a list of equation in a following way but it Mathematica solves equations after 30-40 minutes or don't solve them at all. The functions that I use are ; ...
1
vote
2answers
127 views

steady state conditions

I want to find the steady state value of variables in NDSolve but the variables have oscillation. Do you help me? ...
3
votes
4answers
110 views

Constructing a matrix of solutions using findroot

I would like to solve the following equation numerically: Sinh[y]-(y+Tanh[x])Cosh[y]-y Sech[x]^2==0 I would like to do it by creating a list of x values: ...
0
votes
1answer
45 views

Solve equations and express with specific varible

I have two equations as below: eq1: $8 \pi \gamma r-\frac{4 \pi \text{Delta$\_\mu $} r^2}{\text{v$\_$c}}=0$ eq2: $\text{Delta$\_\mu $}=\text{K$\_$b} S T$ When I try ...
1
vote
1answer
68 views
3
votes
1answer
120 views

Randomly generate points on a van der Waals surface

I'm looking to randomly place an atom $\mathbf{A}$ onto a van der Waals surface formed by atoms $\mathbf{B}$, such that the distance between the randomly-generated atom $\mathbf{A}$ and the nearest ...
3
votes
0answers
124 views

How to solve partial differential equation

How to solve in Mathematica this partial differential equation: $0.5\frac{\partial t(x,y)}{\partial x}+1.5\frac{\partial t(x,y)}{\partial y}+t(x,y)=y\cdot \sqrt{1+x^{3}}$ with condition $t(1,y)=y+2$? ...
1
vote
2answers
58 views

ParametricNDSolve and NDSolve inside Manipulate environment

I have a system of three coupled differential equations that can be pretty readily solved by NDSolve: ...
5
votes
4answers
212 views

How to find a starting value that is closer to the solution?

I am trying to solve the following system. Firstly I have a table of numerical values I will call numbers ...
0
votes
1answer
88 views

solve equations

I want to find the solution of these equations: ...
2
votes
4answers
335 views

solve equation with loop

I want to solve equation with different variable and list answers in a table how can Solve it in a loop (Without repeating the equation) ...
1
vote
1answer
79 views

How to input equations for Solve

I'm trying to input: $$\log_{\sqrt 3}\frac{7-2x}{x+3}-\log_{\frac{1}{\sqrt 3}}(x+3)=\log_{\frac{1}{3}}9$$ My try: ...
5
votes
1answer
66 views

How to solve an equation system whose equations are based on Mod[x,y]

I'm trying to find the parameters of a specific linear congruential generator (pseudo random number generator) based on a list of the first five numbers generated by it. The list is this one: ...
1
vote
0answers
174 views

Help with calculating a complicated integral

Edit: The question is solved : )) Thank you for your attention ! I am sorry for mass questions, but the question bothers me a lot. So I would like to ask this question here. This problem arises when ...
4
votes
2answers
69 views

Find Instance with Set Membership Condition

Given two vectors $u=(x_1,\ldots,x_n,a_1,\ldots,a_s) \in \{-1,1\}^{n+s}$ and $v=(x_1,\ldots,x_n) \in \{-1,1\}^n$ and a bunch of fixed vectors $c_1,\ldots,c_k \in \{-1,1\}^{n+s}$ and $b_1,\ldots,b_k \...
3
votes
2answers
107 views

How do I find the intersection points of two piecewise functions? [closed]

I've got a piecewise function that is defined as follows: ...
2
votes
1answer
146 views

Problem with implementing Regula Falsi [closed]

I checked the "Questions that may already have your answer" and didn't really find what I need. It's actually pretty basic. I want to solve an equation manually with Regula Falsi. I dont need a ...
6
votes
3answers
74 views

Using Select on a 2d table with a criteria that accepts 3 parameters

I have a table sets := Table[{i, j, k}, {i, 1, 10}, {j, 1, 10}, {k, 1, 10}] and I want to use a function that accepts three parameters and returns a boolean, as ...
0
votes
1answer
111 views

Solve failing to solve system of two polynomial equations

I have two equations: $$P_a=P_a(x,y)$$ $$ P_b=1-P_a(x,y) $$ $P_a$, $P_b$, $x$ and $y$ are probabilities so their values are between 0 and 1. If I know the values of $x$ and $y$ I can calculate ...
2
votes
0answers
130 views

Can equation solving be done in parallel?

I'm solving a set of equations that look like: ...
1
vote
0answers
106 views

Solving a set of trigonometric equations [closed]

I've been trying to solve the following equations in order to plot Subscript[θ, 41] with respect to Subscript[θ, 2] from 0 to ...