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

learn more… | top users | synonyms (4)

3
votes
1answer
275 views

HarmonicNumber problem

I am looking for all the roots of HarmonicNumber, in the domain [-30, 1] and [0, 6000] for the real and imaginary parts, respectively, and where the parameter ...
3
votes
2answers
412 views

How can I get the exact real solution of this equation?

I want to solve the equation Sqrt[x] + Sqrt[1 - x^2] == Sqrt[2 - 3 x - 4 x^2] with real solutions (in the real domain). I tried ...
0
votes
0answers
69 views

NIntegrate: integrand has evaluated to non numerical values

I have pasted a code that has been giving me some trouble and errors when I try to compute. ERROR: "The integrand 1435.1232 E^(-6.4703566*10^6 s^2) deEntrance[s,phi]^2 has evaluated to ...
0
votes
1answer
160 views

How can I obtain the complex root of an equation with FindRoot

I want to obtain the complex roots of some equations that are similar,but each of them has a different condition. this difference is the value of α in these ...
0
votes
2answers
146 views

Solving a system of equations using matrix form

Please bear with me as I am a beginner at Mathematica. In the following system, all variables on the right hand side are known, except for w1, ...
-3
votes
1answer
64 views

Finding integral bounds

i have this integral shown below is equal to 1, and i need to find "a" on mathematica, but I'm not sure how. integral (from 0 to a) sqrt((-50.8938 sin(8.4823 t))^2+(4-11.3097 sin(11.3097 t))^2) dt = ...
1
vote
1answer
114 views

Find all roots in the interval of nonlinear equation

I am struggling on how to find all the roots of 1+1/2^x+1/3^x==0 which lie in a given of real and imaginary interval. Solve ...
0
votes
0answers
75 views
1
vote
2answers
141 views

NSolve for high degree univariate polynomials

I am trying to solve a high degree univariate polynomial using Mathematica's NSolve command. But when I plug the solutions generated by Mathematica back to the equations, the equations are massive ...
0
votes
1answer
38 views

Using NDSolve with coupled ODE [closed]

I am trying to solve a simple coupled ODE in Mathematica but an error keeps on popping. I am very new to Mathematica. ...
2
votes
1answer
351 views

Solution given by Wolfram Alpha but not _Mathematica_

Why will Mathematica not give a soluion to Solve[Log[x] == Log[j, Log[j, x]], j], but Wolfram Alpha will?
3
votes
1answer
147 views

Control over the way matrix is displayed

I am wondering how to change the output format in Mathematica. For example, I have $x=\binom{3}{1}$ and $y=\binom{2}{5}$, and I want to find what linear combination of $x$ and $y$ produces ...
0
votes
1answer
55 views

Inequality test returned unevaluated

I tried, Refine[Sin[k]^2/(k^2 + k + 1) < 1/(k^2), Element[k, Integers]] $\frac{\text{Sin}[k]^2}{1+k+k^2}<\frac{1}{k^2}$ It returns unevaluated. I ...
0
votes
0answers
47 views

Code for solving numerically an integro-differential equation

First of all, I want to greet the community. This is my first question, but I hope I will be able to help answering others members questions, although I am quite new working with Mathematica. I would ...
0
votes
3answers
173 views

Solving One Equation with Two Variables

I am trying to solve an equation with two variables. It is the last step in the process of using the method of undetermined coefficients to solve a nonhomogeneous differential equation. The equation ...
1
vote
0answers
33 views

Determine Functions Given Data Points [duplicate]

Is it possible for Mathematica to solve for f(x,y) = 0 such that {x,y} contains {{0,0.5}, {1,0.5}, {0.6,0.8}, {0.4,0.2}} ? Do we need to specify f(x,y) first ? ...
0
votes
1answer
79 views

Solving a system of equations with variable coefficients

I am trying to solve a system of equation which seems to be simple but much as I tried I couldn't solve it in Mathematica and it says the coefficients need to be exact. Now, I was wondering if someone ...
0
votes
1answer
112 views

Finding solutions of polynomials system

Let $f_1,...,f_n$ be a set of polynomials in $x_1,...,x_n$ with rational coefficients. I need to check whether a system $$f_1=a_1,...,f_n=a_n$$ has a real solution for large enough count of points. ...
0
votes
2answers
148 views

find the real root

I have the following equation: \begin{equation} (y-1)^{b1} - C~~ y~~ \exp(a x)=0 \end{equation} where $a, b$ are real constants, $C$ may be a complex number. I need to find the real solution of the ...
-1
votes
2answers
46 views

single root of a cubic function

As it can be shown that the function f(x)=3x^3-9x+1 has a single root in the interval abierto (0,1). Try to solve using Newton Raphson method, but that is more than a demonstration calculation
1
vote
1answer
130 views

How to solve a complicated equation system

I am trying to solve the equation system eq1==eq2 for $\sigma1$ and $\sigma2$ where eq1 and ...
0
votes
1answer
173 views

How to use `FindRoot` to solve an equation containing a parameter?

I'm trying to derive some of the results of the following paper: Electrodynamics of semiconductor-coated noble metal nanoshells, JT Manassah - Physical Review A In the paper there is matrix $\mathbf ...
0
votes
1answer
57 views

FindRoot finds a solution not found by NSolve

I am trying to solve a polynomial equation of higher order with non-integer exponents. When the order of the system is greater than 4, FindRoot provides a correct solution that is not found by NSolve. ...
3
votes
3answers
153 views

How can I find the boundary function in RegionPlot?

I have a problem with finding the function that gives the boundary curve in RegionPlot comamnd. I use the following code to make the regions in which two ...
2
votes
1answer
101 views

Finding the roots of a function with a parameter

I am using a differential equation method for finding the roots of a function. My function is much more complicated but I can illustrate my problem with a trivial example. The problem occurs when ...
6
votes
2answers
292 views

Why does Equal[“string”, False] not evaluate to False?

Why does Equal["string", False] not evaluate to False? I would have thought Mathematica could prove that these two things are ...
3
votes
1answer
96 views
0
votes
1answer
113 views

Finding the first five eigenvectors and values for a 500×500 matrix

I'm trying to find the first five eigenvalues and vectors of a matrix that has the following proporties: ...
0
votes
0answers
64 views

System of differential equations - solving for a constant

I will reformulate my question in the hopes it will be more intelligible. First, I defined the functions: ...
1
vote
0answers
115 views

Finding Values of All Nine Constants in q-hypergeometric Equation

I suspect that an identity of the form $$\sum_{j=-n}^{j=n}(-1)^jq^{j(5j+1)/2}=\sum_{r=0}^{n}f_{ar+bn+c}(-1)^{n-r}q^{(n-r)(dr+en+f)/2}\frac{(q;q)_{gr+hn+j}}{(q;q)_{n-r}}$$ for $a, \dots , j$ integer ...
3
votes
1answer
171 views

Strange behavior of Reduce with a cubic equation

This equation: $(\frac{-a}{x})^2=\sqrt{\frac{1}{x}}$ at $a > 0$ and $x > 0$ has a clear solution $x=a^{4/3}$, doesn't it? However, ...
0
votes
1answer
170 views

Center Manifolds

...
8
votes
2answers
155 views

How to correct this, `f[a_] := FindRoot[eq == 0, {x, 0.5}]`, where `eq` contains a parameter $a$, without using `eq[a]`?

I want to solve an equation with a parameter $a$, and define the result as a function of $a$. It is something like this: ...
0
votes
2answers
43 views

how to define roots of an equation as a function? [closed]

I need to solve an equation depending on 3variables in only one variables and define the roots as a function of the remaining variables? I used some thing like that: ...
2
votes
1answer
87 views

why doesn't NSolve find all the solutions that Solve finds?

Define d[p1_, p2_] := (p1 - p2).(p1 - p2) to be the square of the distance between two points. I am trying to solve equations like: ...
2
votes
2answers
82 views

Graphical solution of a a two-variable system containing an equation and an inequality

I'm currently studying atmospheric-gravity waves and their dispersion relations. I want to have look at values of $(x,y)$ that solve the following system : \begin{equation}\label{}(1) \left\{ ...
0
votes
0answers
53 views

Can't Solve a system of differential equations, Solve takes too long

My question is probably not really interesting but I really need help on this because I won't have access to a more powerful computer. So my model contains 7 equations : ...
1
vote
2answers
141 views

Solve within a range?

Is it possible to solve an equation in which some some of the parameters have defined ranges? Example: ...
1
vote
2answers
227 views

Projection of curve 3D (x,y,z) on the x-y plane

I have a following systeme : \begin{equation} \left\{ \begin{array}{rcr} (\beta+\frac{1}{2}\delta^{2})\nu_{1}(u)-\delta\nu_{2}(u)+\nu_{3}(u)& = &0\\ ...
1
vote
0answers
38 views

RSolve works slow and does not give an analytical solution for solving high order linear difference equations

RSolve@@{{a[n]-a[n-10]==101}~Join~Table[a[i+1]==101+10i,{i,0,9}],a[n],n} I want to get the exact form of general formulas, but ...
0
votes
2answers
68 views

Symmetric function of the roots of a polynomial

First, I'm a beginner. I can compute the sum of roots with the follwing: Roots[x^7 + 5 x^6 + x^5 + x + 1 == 0, x] Plus @@ (x /. {ToRules[%]}) // Simplify Of ...
3
votes
3answers
179 views

Can Mathematica solve $x^{b^2} + ax^b -1 = 0$ for $x$ with $a>0$, $b>1$?

I have a problem that I can't seem to solve neither analytically nor with Mathematica. Namely, I have the expression $$x^{b^2} + ax^b - 1= 0,$$ which I want to solve for $x$ with $a>0$, $b>1$. ...
0
votes
0answers
85 views

Solve function doesn't work

I have the following system of equations that I need to solve: ...
0
votes
1answer
147 views

Nonlinear system of equations

I have been working to find an equilibrium solution for a Hamiltonian dynamical system. I have reduced the problem to the simultaneous solution of 3 equations: ...
0
votes
1answer
63 views
0
votes
0answers
44 views

Ideas for NDSolve?

I'm currently trying to find a numerical solution to a differential equation of the form: D[W[X], {X, 4}] ==(-(1/(delta + G - (G X)/L)^2) + 1/(delta + (G X)/L)^2) ...
0
votes
1answer
80 views

NSolve cannot find the solution

I have some data which looks like: ...
0
votes
1answer
37 views

NSolve stalls when given an equation containing Log

Why does NSolve not work for this type of equation? ...
5
votes
2answers
124 views

What are the Method options Solve command accepts?

What are the Method options Solve command accepts? Solve has the Method option, however documentation contains no methods that it accepts...