Questions tagged [equation-solving]
Questions on the analytic and numerical equation solving functions of Mathematica (Solve, Reduce, NSolve, FindRoot, DSolve, RSolve, etc.).
4,245
questions
0
votes
1answer
20 views
Enumeration of the roots of a polynomial
In Root[f,k], how exactly are the roots of a polynomial f enumerated?
The Mathematica manual seems to only say that
The ...
1
vote
1answer
45 views
Numerically solving an algebraic equation
I have asked a similar question earlier, but I am still stuck at the same problem. I would like to solve an algebraic equation of the form
...
1
vote
0answers
46 views
How to solve this function equation
I can solve the function equation $f(f(x))=x$ with the following code:
WolframAlpha["solve f(f(x))=x", {{"SolutionAsAFunctionalEquation", 1},
"Content"}]
But ...
1
vote
0answers
46 views
Need help in finding intersection point of two function in Block environments
Consider the following model,
u[x1_, y1_] :=Block[{x = x1, y = y1}, ODE
f = Sin[c x + y]; g=(c 5 y + 2)/(x + 2);s1 = Solve[{f == g}];{s1}]
and then call the <...
0
votes
1answer
47 views
Find an instance of a Kaprekar number
Here are two instances of an Kaprekar number
$\text{9${}^{\wedge}
$2 = 81 $\&$ 8+1=9}$
$\text{8${}^{\wedge}
$3 = 512 $\&$ 5+1+2=8}$
There are certainly more with a higher exponent , ...
1
vote
0answers
39 views
Solving a system of trigonometric equation embedded inside module for multiple times
\begin{align*}
u_{1}&=c_{1}cos(\beta x)+c_{2}sin(\beta x)\nonumber\\
u_{2}&=c_{3}cos(\beta (x-z_{1}))+c_{4}sin(\beta (x-z_{1}))\nonumber\\
u_{3}&=c_{5}cos(\beta (x-z_{2}))+c_{6}sin(\beta (...
2
votes
1answer
43 views
How to make sure NSolve gives all solutions in a given range?
When I input the system of equations:
...
1
vote
1answer
52 views
Gauss-Seidel method
I am trying to solve a system of equations with Gauss Seidel method.I reached this point but there is some problem,and I can't find a result.This is the system.
...
2
votes
2answers
86 views
How to find the variational result of this functional according to the definition of textbook
I see this variational problem here.
The functional is :
$$J(y)=y^{2}(x_{0})+\int_{x_{0}}^{x_{1}}(xy+y'^{2}) dx$$
In the textbook, the result of finding the functional variation according to the ...
3
votes
2answers
429 views
Solving an equation approximately
I have a complicated equation in terms of $\omega$ and $\kappa$:
...
0
votes
0answers
20 views
“not a quantified system of equations and inequalities” problem
I am trying to calculate a system of (almost) linear equations. I have 10 equations and 9 variables (first 10 lines in the Solve function), so it should be possible.
...
2
votes
1answer
43 views
Find transfer function from system of equations
I have a system of equations, For example:
eqns = {a1 x + b1 y + c1 z == d1, a2 x + b2 y + c2 z == d2, a3 x + b3 y + c3 z == d3};
and for this I need to find <...
2
votes
1answer
59 views
How to convert linear equation to slope-intercept form? [closed]
Is there a general way (that can be applied to other linear equations too) to convert linear equation to slope-intercept form?
For example, I have linear equation:
$ 6x+3y=5 $
I want a method that ...
2
votes
1answer
76 views
Help: Obtain a huge amount of data solved in FrobeniusSolve? (perhaps better without running FrobeniusSolve?) [closed]
How to obtain a huge amount of data solved in FrobeniusSolve more systematically?
I am interested in obtaining these two sets of data from FrobeniusSolve:
...
2
votes
2answers
200 views
Got Solutions to a set of non liner equations in Matlab but not in Mathematica. Why?
I was trying to solve a set of non linear equations using NSolve in mathematica. I got a result saying that no solution( {} ). My friend tried it in Matlab he was able to get a solution to the same ...
1
vote
0answers
32 views
fuzzy linear advection equation by finite difference methods [closed]
i need to write acode for solving advection equation in one D , i needd for single parametric . how i can do that by using finite difference methods such as upwind and leapfrog?
0
votes
1answer
35 views
Finding roots of a non linear function - Working precision and accuracy goal error
Consider the following function
...
1
vote
0answers
32 views
Systems using Round cannot be solved with methods available
I have a simple system for which I would like a solution:
$\text{round}(a \cdot x^2 + b \cdot x + c) = \text{round}(x^2)$
Even simpler (for purposes of debugging), consider this special case:
$\...
1
vote
1answer
47 views
How do you find the x-intercepts of a quadratics -1 + 3 x - x^3 [closed]
How do I find the intercept of -1 + 3 x - x^3? when I use solve it gives me imaginary numbers and 'Reals' doesn't work either but when I plot it there is an x intercept
1
vote
0answers
57 views
problem with solving inequality $x+1/x>-1+1/x$. different answer in Mathematica and Wolfram Alpha
I tried to solve inequality $x+1/x>-1+1/x$ with Wolfram Alpha, and it gave me the answer $(-1,0)\cup(0,+\infty)$. This is correct.
But when I try to solve it in Wolfram Mathematica 12.0 (with ...
1
vote
1answer
68 views
Solving an equation for a power of unknown variable
How do I solve an equation for a power of $t$, e.g. solving
$$-t(x–8)/8 = –2(x+4)/t$$
for $t^2$ instead of $t$, i.e. to get the answer
$$t^2=16(x+4)/(x–8)$$
from ...
0
votes
0answers
76 views
Solving equations using Implicit-Runge-Kutta method
I am trying to solve the system of equations using Implicit-Runge-Kutta method but mathematica is showing error "NDSolve::ndcf: Repeated convergence test failure at [Tau] == 4.9`; unable to continue."....
0
votes
0answers
52 views
Small issue with PDE initial condition
I'm trying to solve the Fokker-Planck equation
$$\frac{\partial p}{\partial L}(L, \eta)= \frac{\partial}{\partial \eta}\left[\left(\eta^{2}-1\right) \frac{\partial p}{\partial \eta}(L, \eta)\right] = ...
1
vote
1answer
59 views
Problem with Solve and PrimeZetaP
I assume this is something to do with limits on numerical precision, but can someone explain the difference in output between these two Solve problems:
...
2
votes
2answers
53 views
How to use NIntegrate inside FindRoot?
I am trying to use FindRoot on functions that involve NIntegrate, and Mathematica is throwing undesirable errors even when it ...
1
vote
0answers
53 views
Solving a system 15 Equations to find transition probabilities [closed]
I'm trying to find a decimation-invariant random walk on a certain fractal. As a result I'm trying to solve a system of about 12 equations including equations like:
In this case ...
0
votes
1answer
34 views
Extract solutions in an interval for a trigonometric equation
Consider the solution
x1 = x /. Solve[{Cos[x] + Sin[x] == 0}, x]
The output is a conditional expression or, with //Normal, a ...
3
votes
1answer
177 views
How to calculate the degree of $∠FEB$ under this geometric scene
I want to calculate the $∠FEB$ in the figure below, but I can't solve this question with GeometricScene function.
What can I do to find the answers to these ...
0
votes
1answer
123 views
Help with implemented Piecewise in Module
Suppose we have an ODE in the form:
f''[r] + f'[r] == t f[r]+h[r]
where
...
0
votes
0answers
45 views
I want to plot root of the following complex equation
I am trying to plot the roots of the following equation as mentioned in the code below But it is not giving me output. If anyone can resolve this problem for me is most welcome.
...
1
vote
1answer
96 views
How to plot root of the complex equations
I want to plot the roots of the complex equation of a1. I have tried the following code but this is not giving me any result. I need bistable plot. How it is possible.?
...
0
votes
1answer
44 views
Help with printing table data
I am looking for the way of building a Table in a fast way. My true table evaluates huge functions with a system of differential equations . Let us for simplicity consider this:
...
3
votes
3answers
164 views
How to solve an equation on a given relation
I was wondering whether it was possible to solve a linear equation in two unknowns for a specified relation of the two unknowns, meaning that, given
$$x+y=\alpha x+\beta y+\gamma$$
I want to have $x+y$...
0
votes
0answers
40 views
Trying to solve an equation without success
I'm trying to solve the following equation
(1-b)(y^(f-1)f)/(1+y^f)-((c+b)(1-a))/(1-y) = 0
for y. It looks simple enough, but Solve only gives me a solution where ...
1
vote
1answer
20 views
cannot get EvaluationMonitor to output number of iterations taken to find a root
I was given the following problem:
Consider the equation x = exp(-x2). Plot the two curves on the same plot to get a rough idea of the intersection point. Then use a built - in function (e.g. ...
2
votes
2answers
343 views
How to solve a system of transcendental functions?
Having difficulty solving the following instructions:
Solve the system of simultaneous transcendental equations (e^x+ ln(y) = 2 ; sin(x) + cos(y) = 1). Hint: Look for a solution pair (x,y) that meets ...
17
votes
2answers
339 views
3D Elastic waves in a glass
Take an empty glass, hit the side, the glass will make a sound that can be recorded using
...
2
votes
2answers
95 views
How to use the algorithm of dynamic programming to find out the optimal selection scheme of this knapsack problem?
Take out a certain number of items from M items and put them in a bag with a space of W. the volume of each item is V1, V2 to Vn, and the corresponding value is P1, P2 to PN. The quantity of each item ...
1
vote
0answers
57 views
Find element in Integers satisfying certain equation
I'm trying to find $x$, such that
$$4 \cos ^2(x)\in \mathbb{Z}.$$
I tried two methods:
NSolve[4 Cos[x]^2 \[Element] Integers, x]
and
...
0
votes
1answer
42 views
1
vote
0answers
43 views
Interpolating a density plot
I am solving a complicated series of equations (involving FindRoot and PolyLog), and finally I get this plot
Code here:
...
2
votes
1answer
71 views
Solve not finding a solution
Solve is timing out while trying to compute:
Solve[(b*((Α^a*Β^b*Γ^c)/((β+Β)^b*(γ+Γ)^c))^(1/a))/(a*β+a*Β)==Ν/Μ,β]
For particular choices of a,b,c it will find a ...
0
votes
0answers
43 views
Reduce taking a long time
I am delving into proving subspaces of polynomials.
The following did not finish after several minutes on v.11.3, and took 23 seconds on v.12.0:
...
0
votes
1answer
44 views
Hyperbolic Second Order PDE - boundary condition with sinusoid
This is similar to countless PDE equations, but the error seems specific to my case:
I'm trying to solve a hyperbolic PDE, where $U=(x,t)$ and $V=(x,t)$:
The system represents a piezoelectric beam ...
2
votes
0answers
39 views
Set Underflow precision in Mathematica 12 same as version 11.x [duplicate]
It seems like Mathematica version 12 sets arbitrary underflow precision depending on the function, but I would like the underflow precision to be same as what was for previous version of Mathematica ...
0
votes
1answer
105 views
Solving a system of Non-linear equations by Fixed Point method or Newton Raphson method
I have a system of five equations with ten variables, i.e., the radial distance $r$, polar angle $\theta$; four spin vector components ($St, Sr, S\theta, S\phi$) and four momentum components ($Pt, Pr, ...
1
vote
0answers
44 views
FindRoot giving error in Mathematica version 12
I was using the same code in previous version of Mathematica but unfortunately I had to update Mathematica to version 12 because I upgraded MacOS to Catalina. Now when I run my code, I get this error
...
2
votes
1answer
32 views
How to chop complex number from solution solve using a model
Hi I have a set of 4 solution that was solved using a 4th order polynomial equation.
I have noticed that some of the real number solution occurred through the list of 4 set of solutions.
I have ...
2
votes
2answers
59 views
Using Reduce to solve trig equations. Error: unable to decide whether numeric quantity .. is zero
I'm trying to find solutions to a fairly simple pair of simultaneous equations in variables $\phi_1, \phi_2$ using Reduce.
...
0
votes
2answers
91 views
Assign FindRoot output vector to a vector instead of element by element
Using FindRoot to solve a multivariate equation system, assigning the output to variables one by one works, but assigning the output vector to a vector gives the ...
