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

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5
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0answers
213 views

Strange behaviour of NotElement in Reduce

Bug introduced in 8.0 or earlier and persisting through 10.4 or later Confirmed, as bug, by WRI: [CASE:3527549] I have observed curious behaviour on domains supplied to ...
2
votes
1answer
109 views

Issue with NSolve for solving six equation and six unkown [closed]

I am trying to solve the following six equations and six unknown but It takes me one hour then the program stops. Would you please give some help. I am a beginner. $eqe1=0.000466667 \left(A_2 \cosh (...
0
votes
1answer
51 views

Simple grouping equations [closed]

I'm new in the Mathematica world. A very basic question. I have been using the command Eliminate on a set of equations as follow: ...
0
votes
0answers
41 views

Using Solve with NIntegrate [duplicate]

I have a function defined as a numerical integral of a parameter. When I try to solve for the parameter Mathematica complains that the integrand has evaluated to a non-numerical value (which makes ...
0
votes
1answer
81 views

How can I calculate the root of any order of power series

How can I calculate the root of any order of power series with Mathematica. Here I insert every quantity by hand. But I want to give a, ...
0
votes
1answer
59 views

Eliminate variable on multiple equations [closed]

I'm pretty new with Mathematica. I have to perform a really simple operation, but I'm really struggling with that. I have a set of 4 equations, for example (they can also be more complex): $ AA = 2 ...
0
votes
2answers
66 views

How to find the value of a variable using solution of Simultaneous equations? [closed]

I have to find the value of p where p=a1*x+b2*y; using the solution of the equation ...
2
votes
1answer
112 views

How do I find the analytical roots of this polynomial? [closed]

I want to find the analytical roots of this polynomial - x - a^3*x*(a^2*x*(a*x*(x - 1) + 1)*(x - 1) + 1)*(a*x*(x - 1) + 1)*(x - 1) ...
0
votes
1answer
39 views

Transform system of equations while leaving solution set invariant?

Consider the example system of equations syst==res where syst={x + 2 y + 3 x y, 1 + 4 x + y}; res={0 , 0}; Solving for the ...
1
vote
0answers
48 views

Solve Two Functions In Three Variables and use ContourPlot [closed]

I am solving this system in mathematica ...
0
votes
1answer
45 views

Simplify doesn't simplify multiple conditions from Reduce

Consider the following simple example where I try to solve an equation and then apply a bounded interval to find the right result out of an infinite amount of solutions: ...
2
votes
1answer
128 views

FindRoot of interpolating function from NDSolve

I am having issues finding the root of an interpolating function obtained from NDSolve. For example: ...
2
votes
2answers
239 views

Simultaneous equations—classify the solution set as finite, infinite, or none [duplicate]

How do I find the values of $b$ and $c$ for the equations $x + 5 y = 4$ and $2 x + by = c$ with a unique solution, an infinite set of solutions and no solutions with Mathematica?
1
vote
1answer
60 views

Solving a simple trigonometric equation in a range

I would like to solve a simple trigonometric equation, for example $\sin\theta=\frac{1}{2},$ but Solve gives the single solution obtained by using the inverse ...
0
votes
2answers
114 views

Finding all complex polynomial roots in a specified range efficiently

I need to find the roots of a rational polynomial that are near i. In the following code, I try that two different ways. First, I use a constraint to only find roots in the right region. Second, I ...
1
vote
1answer
157 views

How do I plot this (x^3 - 2*x)^Ln[x]? [closed]

y=(x^3 - 2*x)^Ln[x] I'm totally clueless. I tried with y=e^(Ln[x] Ln[-2 x + x^3]) by Ln-ing on both sides but there is ...
1
vote
0answers
52 views

Strange behavior when solving absolute value equations

Try this: Solve[Abs[x/2 - 1/3] == 1, x] Produces this answer: (* {{x -> -(4/3)}, {x -> 8/3}} *) Now try this: ...
0
votes
0answers
89 views

Help numerically solve this non-linear PDE with singularity

I have trouble finding a numerical solution to the partial differential equation below. It seems to be a singularity in the solution somewhere, so I searched online and found that it is suggested to ...
14
votes
3answers
432 views

Is there any predictor-corrector method in Mathematica for solving nonlinear system of algebraic equations?

The FindRoot Function in Matheatica can easily be used to solve systems of nonlinear algebraic equations. But, I want to solve a system of nonlinear equations with variations of some parameters. ...
1
vote
1answer
103 views

Solving equations with subscripted variables

A student of mine tried: Solve[1/R == 1/Subscript[R, 1] + 1/Subscript[R, 2], R] which did not work. We then tried: ...
0
votes
0answers
29 views

Quickly Solving a High-Order Root System of Equations of Arbitrary Form

I have the following system of equations that involve some rather complicated exponents: $$ \left\{\frac{\mathit{a} \sigma ^{41/34}}{\mathit{m}^{8/119} \mathcal{M}^{28/17}}=1,\frac{\mathit{b}\mathit{...
1
vote
1answer
71 views

I can not solve this equation for recurrence [closed]

Use RSolver to solve RSolve [{f [n + 1] == f [n] + 2 n + 1, f [1] == -3}, f [n], n] but I do not get solution Edit my solution
0
votes
0answers
46 views

How to get x = 1.234 from {x -> 1.234}? [duplicate]

I'm a complete beginner in Mathematica (started a couple of days ago). I've solved a function using "Solve" and the result is this one: Out[1] = {x -> 0.000942939} How do I get the 0.000942939 ...
0
votes
0answers
86 views

Solving numerically a system of equations using different methods

I will use, as an example, the simple Henon-Heiles potential ...
1
vote
2answers
102 views

Bessel-like equation problem with NDSolve

I am trying to solve the following nonlinear ODE, but Mathematica takes forever to give a result. Any idea why? ...
9
votes
2answers
204 views

NSolve finds real-valued results in version 9, but not in version 10

UPDATE Reals also was used in the code. Actually, I tried the following simple piece of code. ...
1
vote
1answer
62 views

how to replace one calaculation result to another one in a loop?

I am doing the calculation in a loop. I gain a digit for rzin in ...
1
vote
1answer
51 views

Approximating exponentials in a nice to read format

I need to make some approximations, basically I have something like $$ e^{i*a} = -0.735145 + 0.67791*I $$ and I want to approximate this to something that is easily readable, like $$ e^{\frac{3*\...
0
votes
0answers
49 views

Combining two NDsolves results in “The search has encountered a complex value…” and no solution

So far I used to seperate NDsolves to solve a system of coupled differential equations, where the first NDsolve yields the Boundary conditions for the second NDsolve ...
4
votes
3answers
445 views

Solving complex equations with variable exponents

How would I go about solving $(1+i)^n = (1+\sqrt{3}i)^m$ for integer $m$ and $n$? I have tried ...
9
votes
1answer
207 views

Using Solve to solve the equation $x^{1/3}=-1$

I am curious why this command returned no answers: Solve[x^(1/3) == -1, x] Gives this output: (* {} *) I was able to get ...
3
votes
3answers
263 views

Number of solutions for inequality

Please explain me how can I calculate a number of possible solutions for such inequality and obtain those values: 3x + 7y + z <= 198 where ...
0
votes
1answer
71 views

Integrate over FindRoot solutions

I have a function of bivariate normal PDF and its marginals defined as ...
0
votes
0answers
66 views

Eliminating one function from non-linear PDE

Is there any solution to eliminate function p[x,y] from these two equations which are equal to zero (diff1=0 and diff2=0) where c and d are constants. I need one equation where should figure just w[x,...
0
votes
0answers
36 views

Symbolic root computation of a function that depens on parameters

I'm given list of real numbers $a_i, i=1,N$, where usually $N \le 100$. Consider a function $f_N = f_N(x,a_1,...,a_n)$. I need to find the roots of $f_N(x)$ on $[-1,1]$, assuming that $a_i \notin [-1,...
13
votes
2answers
272 views

Heat convection differential equations from 1952 - Mathematica “fails to converge”

I am trying to solve a fundamental problem in analytical convective heat transfer: laminar free convection flow and heat transfer from a flat plate parallel to the direction of the generating body ...
3
votes
1answer
145 views

How to speed up filling a matrix as much as possible in a loop?

In order to find the solution of an $n\times n$ system of nonlinear equations by the method $x_{k+1}=x_k-D_k^{-1}f(x_k)$ where $D_k$ is an approximation of the Jacobian and defined by \begin{equation}...
1
vote
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
86 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
67 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
47 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
58 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
72 views

SolveAlways 'never' completes

After allowing Mathematica to run on ...
2
votes
1answer
83 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
186 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
106 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)&...