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

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0
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1answer
183 views

Solving a single-variable equation mixed with exponential and algebraic

Trying to solve for x Solve[((a - 1) (1 + d x^2))/(a (Exp[b x + c] - 1)) - e == 0, x] in terms of the constants a,b,c,d, and e. Mathematica says "This ...
1
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2answers
201 views

Solving for the limits of an integral

I am trying to get Mathematica to solve for the symmetric limits of an integral of a Square Wave. ...
2
votes
2answers
131 views

Only one root at specific interval

I need a help to find k here: $f(x)=-k^x + x^2$ It is not too simple. I have interest to find the single value of "k" where, inside interval {x,2,3}, the function have only one value to x when f(x) =...
2
votes
0answers
104 views

Simplify large fractions

Hi i'm quite new with Mathematica and i'm experiencing some problems with Simplify and FullSimplify. I'm dealing with a sistem ...
0
votes
2answers
61 views

How do I simplify an algebraic equation with respect to a specific variable? [closed]

I have the following equation -- which is all in terms of d: ...
0
votes
1answer
71 views

NSolve taking too long to solve system of polynomial equations

I am trying to solve a system of polynomial equations (10 variables and 10 equations) using NSolve in an attempt to find all solutions. ...
-3
votes
2answers
302 views

Solving the symbolic quadratic equation ax2 + bx + c = 0 [closed]

I need to ask Mathematica to solve the symbolic quadratic equation ax2 + bx + c = 0. Does it give you the right answer?
0
votes
1answer
50 views
0
votes
1answer
322 views

How to solve a linear system of 9 equations with 9 unknowns? [closed]

This is my current code and i'm not sure why it's not working. I am new to Mathematica, though. ...
1
vote
1answer
62 views

Error using NSolve function please help

I have tried to use nsolve to solve this transcendental equation for the bound state of a finite well.. For some reason mathematica is just returning my exact input back to me any ideas on how to ...
2
votes
1answer
123 views

Solving for flow speed?

I'd like to use Mathematica to verify the results of a Matlab code that iteratively solves for a flow velocity, u, given some fluid properties and a pressure drop. Ideally, I would like solve the ...
1
vote
2answers
357 views

Why does this expression take a long time to evaluate?

I was just wondering whether there's an easy to see reason for this expression to take a very long time to evaluate: ...
0
votes
1answer
72 views

NDSolve emitting dvnoarg error [closed]

I'm trying to solve this simple system of ODEs, but it gives me the error "The function v1 appears with no arguments". I've attached a screenshot of the code. I hope someone could help me, I really ...
4
votes
1answer
403 views

Very slow mathematica finite differences

I have a simple code which solves an equation by an explicit method (FTCS). It takes mathematica several minutes (mathematica 10.0.2) to finish the calculation while the same code in Fortran runs less ...
1
vote
1answer
107 views

Optimizing matrix inequalities over trace

I need to solve the following problem. Given $n \times n$ Hermitian matrices $A\geq 0$ and $B_1, ~ B_2$ (need not be positive semidefinite), with $Tr(AB_1)<0~,Tr(AB_2)<0$ construct a ...
0
votes
1answer
201 views

FindRoot over a function with some constant variables

I would like to perform the FindRoot command over the function func. Suppose: ...
0
votes
0answers
89 views

Finding roots by solving its ODEs [duplicate]

Roots of fluctuating function (p,q real) needed to evaluate eigenvalues of $$ y(x) = \dfrac{\sin px }{p} + \dfrac {\sin q x }{q} =0 ...(1*) $$ form a real and complex infinite set. The way to ...
1
vote
1answer
155 views

Iteration convergence of Newton approximations

I am trying to determine for which initial values Newton's approximation of specific functions (EX: f(x)=x^2 -1)converge and to what numbers it will converge to. *Where Newton's approximations are x[...
1
vote
0answers
115 views

Solve Lagrange-multliplier with arrow-security prices with nonlinear (exp) utility function

at the moment I have successfully solved the Demand function for securities in the following model: t=0 current time, 2 uncertain states with same probability in period 2 indexed with i=1 and i=2. ...
1
vote
1answer
251 views

Why won't mathematica solve my two simultaneous equations? [closed]

I'm trying to solve for two unknowns with two equations as follows; ...
3
votes
1answer
234 views

Finding all zeroes - mysterious missing roots

Finding all the roots of a function of one real variable has been discussed extensively in e.g. Find all roots of an interpolating function (solution to a differential equation) (answer no. 2 by Jens ...
1
vote
1answer
137 views

Quantum Physics question [closed]

I'm not sure if anyone here would be able to help me. But if you know a more appropriate place where I could ask for help, please let me know. So here's the question: And here's my attempt at ...
1
vote
0answers
89 views

Using Solve without introducing extra variables

First post here. I've tried searching for an answer for this for a few days now, but it seems the search terms (solve, slot, etc) are too generic to be helpful. I'm struggling with understanding how ...
0
votes
3answers
148 views

Delay difference equation

How can I correctly specify and solve a system of delay difference equations in mathematica similar to NDSolve with regard to delay differential equations? For example if I want to "see" the values ...
0
votes
1answer
156 views

Using FindRoot in a Table of Iterations [closed]

So I have a tanh curve and a straight line that cross at the point: msol=FindRoot[Tanh[x] == (T/Tc03) x, {x, 1}] This gives me the roots that I need at a certain ...
0
votes
1answer
54 views

Integrate equation. Variable in terms of another

This might have an easy solution but I am new in Mathematica. I have an equation for which I want to find the solution. My equation goes like: $$\frac{dr}{dx} = \frac{r}{x}\cdot\frac{2}{k\,a^{-2}\,g\...
0
votes
3answers
562 views

How do I solve for the roots of $\sin(x) - x^2=0$? [duplicate]

I have defined h[x] := Sin[x] - x^2. When I submit Solve[h[x] == 0, x], Mathematica tells me Solve::nsmet: This system ...
0
votes
1answer
487 views

solving PDE with periodic boundary conditions

I want to solve a 2D-PDE that has the form ...
-1
votes
1answer
55 views

how to write out this equation on Mathematica? [closed]

I have this equation that my manager would like to use on Mathematica, but I've only been learning how to use Mathematica for a few hours. I need to solve for Ax and also plot a graph. Please help....
3
votes
1answer
148 views

How to solve a transcendal equation

I want to get the solution x of this equation a (-(1/(1 + b c + a x)) - Log[b c + a x] + Log[1 + b c + a x]) - d = 0 in ...
2
votes
3answers
162 views

Solving equation containing Erf expressions

Given the equation below, how do I find the value of b so that the function is equal to 21. I tried solve but I keep getting an error message. ...
5
votes
2answers
192 views

Initial time as parameter in ParametricNDSolve

I need a help with the function ParametricNDSolve. My goal is solve the equation \begin{array} &&\dot{x}(t) = y(t) \\ &\dot{y}(t) = x(t)-1-\varepsilon Cos(\omega t) \\ &x(t_0) = x_0\\ ...
-2
votes
1answer
35 views

Solver for X - with a function [duplicate]

Sorry but I cant figure this out, Someone gave me some help on here yesterday but they didn't show their working so I could not redo what they did when my equation changed. Can someone please help me ...
-2
votes
1answer
96 views

Solve For X inside arc-cos function (with division) [closed]

Very basic but I've been stuck for more than 12 hours trying to solver this equation 20=360/(arccos(X/3200)*2) Can anyone solve X? and explain what exactly you ...
0
votes
2answers
410 views

Nonlinear matrix equation solving in Mathematica

is it possible to solve below equation in Mathematica? A.X+B.Exp[X]==C A, B are square ...
0
votes
0answers
41 views

FindRoot[rhs==lhs, {x,x1,x2}] Vs FindRoot[rhs==lhs,{x,x1}]

What is the difference between these two commands: FindRoot[rhs==lhs, {x,x1,x2}] and FindRoot[rhs==lhs,{x,x1}] They give ...
0
votes
3answers
720 views

Solving system of equations with complex numbers [closed]

I have two equations and two unknowns. The coefficients are complex. How do I solve them using matrices? Or any other method? Here is an example: Trying to find X and Y ...
10
votes
1answer
737 views
2
votes
1answer
150 views

Fixed Points Problem with 2D Mapping

I have been playing with the mapping given by ...
1
vote
2answers
284 views

Trouble using Solve and NSolve with functions involving Erf

I have the following functions: R[k_, x_, t_] := -.5*(k - x)*(1 + Erf[-(k - x)/t]) L[k_, c_, x_, t_] := .5*c*(k - x)*(1 + Erf[(k - x)/t]) I'm interested in ...
0
votes
2answers
98 views

Help Solving A Recusive System: “$RecursionLimit::reclim: Recursion depth of 256 exceeded.”

Was wondering if anyone had any tricks/ideas on solving this system of recursive equations I have. Essentially my goal is to have J2 equal to zero, but to understand how tweaking several parameters ...
2
votes
2answers
160 views

Series expression of a Root object

I was wondering if it is possible to get Mathematica to return a series approximation of a Root object. Example: I want a series representation of x in terms of <...
1
vote
1answer
107 views

Elimination returning true instead of correct answer

I define the following functions: ...
3
votes
2answers
171 views

Numerical root-finding: Find leftmost root in a domain

This is surely a duplicate, but I cannot seem to find a similar question. I use NDSolve to find an InterpolatingFunction y[t] ...
0
votes
1answer
282 views

Solving Integro-Differential equations

I need help solving this equation. Is there a built in function that solves this type of equations? DSolve wouldn't work. Updated equation: ...
1
vote
2answers
154 views

Solving matrix equation

How can I solve the forward equation S[t]=C+A*S[t+1]*(Inverse((I-B*S(t+1)))*A for t=1 to t=10 and ...
5
votes
1answer
213 views

Finding and plotting roots with parameter

I have the following function: $$u(x,t)=\sum_{k=1}^\infty\frac{v_0 L}{\lambda_k c \sin\left(\lambda_k\right)}\sin\left(\frac{\lambda_kx}{L}\right)\sin\left(\frac{\lambda_kct}{L}\right)$$ and this ...
0
votes
1answer
73 views

Elements inside arrays seem to be strings rather than signed numbers

When I have code like b = Array[Subscript[be, #] &, {3, 1}] b = b /. {Subscript[be, k_] :> Subscript[-be, k] /; k > 1} I am noticing that Mathematica ...
0
votes
2answers
268 views

Why does Solve give a wrong solution to an equation? [closed]

I have got a following equation: -(c - x)/Sqrt[b^2 + (c - x)^2] + x/Sqrt[a^2 + x^2] == 0. Trying to solve it for x, so I evaluate ...