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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95 views

Unbounded solution at boundaries with few combination of values in this BVP solution

I had asked a question here regarding solution to a BVP problem. bbgodfrey provided an excellent answer using the method of integrated least squares. However, for a few specific set of values of ...
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16 views

Solve command fails when applied to this equation?

I have the following equation (exp1=1) which i would like to solve for w: ...
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2answers
65 views

Plot the solution and Inverse as well

I used this code to solve an equation and now I would like to plot the solution with its inverse. I can't get some figures?!! ...
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1answer
151 views

NDSolve WhenEvent Partial Evaluation of a Function

I want to obtain an intermediate result from NDSolve using WhenEvent.
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1answer
24 views

Private variable issue in a function environnement

I have the following matrix which represents an input from a .txt file. The first column gives the name of the random variable, the second the probability law, the third the parameters related to the ...
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0answers
36 views

two times DSolve the equations [closed]

I was working those equations but for the second DSolve I have problem?! ...
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1answer
121 views

How can I solve this system of 6 simple quadratic diophantine equations in four variables?

I generated this text file containing tuples $(\sqrt{s}, \sqrt{t}, \sqrt{u}, s,t,u,t+u,t+u-s,t-s)$ where the six variables $s,t,u,t+u,t+u-s,t-s$ are all squares. An excerpt of the data set is: ...
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3answers
153 views

Can I get the given plot without calculating the roots numerically? Is it possible to use Manipulate/Animate to get a continuous line of the points?

I have two functions $F(x,y)$ and $G(x,y)$ for $0<x\leq3$ and $-1\leq y \leq1$. Given a specific value of $y$, I want to find those values of $x$ for which we have $F=0$ and $G\neq \pm 1$. For ...
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2answers
147 views

How do we solve this system?

consider: \begin{align} \dot S &= A-\beta S(I+\rho_1 T)-(\mu+p)S\\[1ex] \dot V &=pS-\rho_2 \beta V(I+\rho_1 T)-\mu V\\[1ex] \dot L &=l \beta S(I+\rho_1 T)+\rho_2 \beta V(I+\rho_1 T)-(\mu+\...
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0answers
45 views

2 equations 2 Unkowns at loop variable input [closed]

I want to solve a system of equations 2 equations 2 Unknowns at loop variable input at the equations how could I do that ?
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1answer
76 views

NSolve syntax for region

I am trying to solve these simultaneous system of equations only in a specified rectangle going from -100<x<100 and -100<y<100. But I think I am making a syntax error and hence I m not ...
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2answers
98 views

LinearSolve with 4 variables and 3 equations [closed]

Is it possible to find a solution or at least run LinearSolve when there are 4 variables and 3 equations. For example: a + b -3c + 4d = 4; 2a + 5b -6c +2d = 15; 3a -4b + 5c -3d = 10.
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75 views

A problem when solving an equation with symbolic variables

I asked a question a couple days ago and received a solution that worked for me at the time. But now I am seeing that the proposed solution fails for some other cases I need. For example, if I just ...
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1answer
57 views

Assumtion on Solve and DSolve

How to fix this problem I can't get something from this!! ...
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1answer
85 views

Symbol of system of equations

I'm wondering if there is a way to use the symbol (the left curly bracket) of a system of equations. So far I found only the following "symbol": I need to remove the two conditions. EDIT2: ...
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1answer
40 views

Using the symbol of the system of equations [duplicate]

Part 1 I'd like to know how to use the symbol of system of equations (left curly braces). I tried the following code: Part 2 How can I add a third equation?
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1answer
59 views

How to find constrains on variables that make a system of inequalities not have a solution

My problem is as follows: How do I ask Mathematica the following question. Let $f(x,y,z,a,b)$ be a 5 variable polynomial. I want to find all values of $a,b$ for which $f$ has no zeros in the region $...
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1answer
86 views

Non- linear ODE

I was working on this equation but I can't get out something for this: ...
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1answer
52 views

How to obtain exact answers for casus irreducibilis for third order equation in Mathematica

According to https://en.wikipedia.org/wiki/Cubic_equation#General_cubic_formula When a cubic equation with real coefficients has three real roots, the formulas expressing these roots in terms of ...
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1answer
168 views

Using FindRoot[] to find an inflection point

FindRoot[ {Derivative[2][SinIntegral[x]], 0 < x < (Pi)}, x ] I hoped that my code would return a value for x=0 but it is returning an error: "...
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0answers
65 views

How to avoid imaginary numbers as solutions from Sqrt?

test function is the answer that I get from calculating the eigenvalues of a matrix. I need to calculate the square root of it. After I substitute the values for qx and qy, I am expanding it with ...
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2answers
120 views

How do I know Mathematica is doing exact algebra?

I am looking for zeroes of the following polynomial: -36 - 20 a1 a2 + 16 a2 b1 + a2^2 b1^2 + 16 a1 b2 - 20 b1 b2 - 2 a1 a2 b1 b2 + a1^2 b2^2 in the region ...
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2answers
171 views

Is it possible to find a non-zero solution of an ODE?

Is it possible to solve the 4th-order ode analytically? ...
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1answer
39 views

Reduce relations with Fibonacci function never terminates,

i have a reduce operation which includes Fibonacci function. but the problem is it never terminates, i tried some modifications, for example removing f1 in my relation. sometimes it works and at least ...
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1answer
57 views

ODE solution for a simple case

I was trying to solve this but I can't not fix the problem :( please help me. a,b,f and d positive vale. ...
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1answer
156 views

Show solutions of non-linear equations with multiple variables in 3D space

Consider a (non-linear) system of equations with two parameters x and y and multiple variables ...
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1answer
39 views

FindRoot with Quantities throws error FindRoot::nlnq

I have a fluid mechanics problem, but when I try to solve an equation to get the flow rate Q (m^3/s) it throws an error that I can't track ...
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2answers
88 views

Is task to find intersections of a line and a cubic Bezier curve really so hard?

I wrote formulas for parametric Bezier curves of different orders ...
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3answers
151 views

Challenges and Opportunities of `FindInstance` Command

I'm testing the FindInstance capabilities and ran into one problem that behaves similarly with different types of inequalities. I calculate two points satisfying ...
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0answers
84 views

Solving or Minimizing the Norm of the matrix equation $M^TAM - M^TB - B^TM =C$

I am trying to solve the matrix equation $M^TAM - M^TB - B^TM=C$ where I know A, B and C. My unknown matrix is M which has the special form that all the rows and columns sum to zero. i.e. I have four ...
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0answers
45 views

Equal equations or Expressions

I would like to check if equation (Sigmaa22) is the same as equation (stress) Basically i have 2 equations one is called Sigmaa 22 and the other one is called stress,My problem when i try to check if ...
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2answers
108 views

Mathematica: How can I solve the problem "The Kernel Local has quit (exited) during the course of an evaluation"

I am using a Mac Book with Monterey and 16GB RAM for a calculation with 2 nested For loops. I am relatively new to Mathematika and still trying to learn the language properly, so I hope the problem is ...
2
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1answer
298 views

How to illustrate the optimal solution with kinked constraint?

I have a simple optimization problem with a linear, continuous constraint or a kinked constraint. The optimal solution is either a tangent point with f*<T or at the kink with f*=T. The standard ...
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1answer
79 views

How can I derive all the roots of a complex equation containing the square root of Sinh^2 using Mathematica [closed]

I have the following equation: where m,n are arbitrary natural numbers and beta and k are positive nonzero real numbers. How can I find all the roots of this equation using Mathematica?
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1answer
103 views

How to do Interpolation to this function after given b this values

χ[b_] := (Z/k)*NIntegrate[Subscript[f, pp1][q]*Subscript[F, pp1][q]*BesselJ[0, q*b]*q, {q, 0, b}]; bList = Table[b, {b, 0, 5.1 , 0.05}] where: ...
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1answer
46 views

rewriting the solutions of symbolic 3rd and 4th order polynomials

I have symbolic third and fourth-order polynomials which read. $F_{3}= x^3+p x +q,$ $F_{4}= x^4+p_{0} x^2 +q_{0} x + r_{0}.$ Using the Mathematica, I can find the roots of these polynomials using <...
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3answers
116 views

Root finding in a non-rectangular solution region

If I want to find a root $(x^*,y^*)$ of functions $f(x,y),g(x,y)$ in the rectangular region ${\cal R}=[x_i,x_f]\times [y_i,y_f]$ I can write ...
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0answers
79 views

Solving a linear system with large number of equations

I am trying to solve a system of linear equations having 16 equations and 16 variables. These 16 equations are as below : eqn1 : ...
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0answers
91 views

RootSearch problem when called from within ParallelDo

I have been using Ted Ersek's RootSearch package for Wolfram Mathematica for many years. The package worked great, including inside the ...
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0answers
127 views

Could all eigenvalues of this matrix be positive?

I have the following list $\beta$ with 5 equations ...
4
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2answers
237 views

Using NDSolveValue for Solving a parabolic PDE numerically

Inspired by this question I am trying to solve the following PDE numerically on $x \in [-3, 3]$ and $t \in [0, 0.5]$ using NDSolveValue: $$ \frac{\partial p}{\partial t} = (12x^2-4) p + \left[4x(x^2-1)...
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1answer
67 views

Using Reduce output when multiple variables are identical

Sometimes Reduce produces output where multiple variables are all assigned to each-other for example: a == b && a == d How can I assign this correctly to a ...
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1answer
60 views

Formalization of one optimization problem or solution of inequalities - Part №2

Continuing the question: Formalization of one optimization problem or solution of inequalities Let's consider a more complex problem. We have two polynomial: $p_1=A_2t^2+A_1t+A_0$ $p_2=B_2t^2+B_1t+B_0$...
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0answers
64 views

Is this set of equations solvable?

I am trying to solve a set of equations. I ran it for several days but it's still running. Is this solvable? ...
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1answer
69 views

Formalization of one optimization problem or solution of inequalities

I have polynomial: $p=A_2t^2+A_1t+A_0$ $A_0=(x^2-y^2)+xz$ $A_1=x^2+y^2+z^2+\sin(x)$ $A_2=x^4+y^3+z^2$ $x,y,z$ - parameters, moreover $z$ - the value of which varies in the range $[0,1]$. Polynomial $p$...
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0answers
35 views

Matrix with Gauss method in Mathematica [duplicate]

I need to define a matrix and write code to solve it with the Gaussian method. When I write the dimensions of the matrix, it should be calculated. Could you please help?
2
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2answers
63 views

NSolve not solving within Table

I would like to solve an equation for different parameter values, thus, I used Table[] to create an array of solutions. For some parameter combinations {k,A} NSolve does not give an answer, but when I ...

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