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

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0
votes
1answer
196 views

NDSolve example - analytical vs numerical solution. How to specify initial conditions?

So, I have the following equation: y[t]^-3 == w^2 y[t]/t^2 + y''[t] where w^2 = (t0 k0)^2. Analytic solution is easy to ...
0
votes
0answers
117 views

Mapping the imaginary axis of the complex (s) plane

In this problem is very difficult to analyze the roots s. Firstly I thought that the problem is in precision, but I am not sure. The criterion which I want to obtain is that one of these roots has a ...
1
vote
1answer
47 views

Invariant error plot for an arbitray system of ODE

i try to use InvariantErrorPlot command for a generic system of ODE but i find only example with pre-building equations from Mathematica Packages. This is one of ...
1
vote
1answer
143 views

How to solve that kind of partial fraction decomposition equations? [closed]

I need to find all variables $A, B, C, D$ for given equation with independent variable $s$. How can I solve that with Mathematica ? Example, not working: UPDATE: One Two Three Four ...
4
votes
3answers
185 views

How to find an approximate solution in a region when Solve or NSolve does not work?

Consider the relation x/Tan[Pi x] == y/Tan[Pi y] Solve or NSolve can't give a solution ...
0
votes
1answer
91 views

Numerical method for solving a polynomial equation

I am looking for a numerical solution of a equation which contains, in general, one polynomial equation with unknown variable x. I have tried Reduce, ...
0
votes
2answers
86 views

How to get a number from Solve [duplicate]

It's often useful to get just one number from Solve. I use the following construction for acquiring one solution from the expression returned by ...
0
votes
1answer
86 views

How to Solve/NSolve/Reduce this rationalized equation

In this problem I don't know why the system is not solvable. I have just one unknown K0. ...
0
votes
0answers
65 views

Solving for a variable within a definite integral using FindRoot

I want to solve for P in this equation: Integrate[1/((P/(M*V)) - r*g - c*A*(V^2)*p/(2 M)), {V, 0, 26.82}] = s , where all constants are given except P. I've ...
-6
votes
1answer
110 views

Poincaré section for 3BP

I try to plot the Poincaré section for the 3BP i use the following code that works very well: ...
0
votes
0answers
60 views

How to solve an inequality

I am trying to solve the following inequality: Assuming[{R[k] >= 0, R[k + 1] = R[k] - 2^N Y, Y >= 0 && N >= 0}, Refine[Re[R[k + 1] >= 0]] I ...
1
vote
2answers
134 views

intersection between function and plane

I try to solve a ODE system of equations and i want to plot the intersection of the 3D solutions with a costant plane. To do this i use the follow code: ...
0
votes
0answers
42 views

NSolve or Reduce for obtaining the results and connecting roots

Here I have one problem how to solve numerically equation for different values of one parameter x. I used just two digits because of length, but for x=0.57 I should have one real root and for others ...
0
votes
1answer
160 views

Why can't Mathematica solve this system of equations?

I am trying to solve the following system of equations for three unknowns Theta, Nu, and K. All the other parameters are constants. The third argument in Solve, ...
0
votes
0answers
96 views

Boundary Condition Problem with Green's Function

My temperature distribution looks like: Mean wire temperature is : To[x_] := 2 c1 Cosh[x a1] + a2 And it is continuous at two points. In positive part: ...
1
vote
1answer
146 views

Why Mathematica can't solve this? NSolve or Solve

I want solution of x and y which should be positive real numbers ...
0
votes
1answer
48 views

Solve equation with two different sets of replacement rules

I want to solve eqn for c0. I want to do it with both replacement rules. I realize I could just use solve twice, once for subsCoke, and once for subsPepsi. I'm trying to do it in just one Sovle to ...
3
votes
1answer
91 views

How to transform an equation so that the coefficient of a certain term becomes 1

Say I have an equation like A + 5 B + 10 C == 0 and I want to have Mathematica write this as (A/5) + B + 2 C == 0 i.e., I ...
0
votes
1answer
155 views

Why is my PageRank result in Mathematica converging this way?

I am using this technique to find the PR of these 3 pages. It converges to something it shouldn't be. I tried the same iteration in Java and 2 pages come up with 1.333 and the other one as 0.666. ...
0
votes
1answer
118 views

2 Equations continuous at a point

I want to get continuous point between two equations. My equations are: ...
0
votes
0answers
61 views

Solve gives solution with ComplexInfinity -> number

I am trying to solve a cumbersome equation using ...
0
votes
0answers
31 views

How to Invert a Multivariate Interpolating Function? [duplicate]

I used NSolve on a partial differential equation with boundary conditions to get a numerical solution that Mathematica says is of the form InterpolatingFunction. I then defined a function f(x,y) which ...
4
votes
2answers
175 views

How to set up and minimize a large system of equations to resolve the individual components

I am trying to set up a system of 400*N equations to deconvolute spectral data for four different compounds. I monitored 400 different wavelengths in N solvents (3 solvents in this case). In order ...
0
votes
1answer
114 views

Finding equation of tangent line at a point [duplicate]

my function is defined as f[x_] = x^1.1 - 2.5 x^.5 I need to find the equation of the tangent line to the curve using the point slope form which would be something like f'[a][x+a]+f[a] a=1 and x=1 ...
0
votes
0answers
26 views

FindRoot gives strange results when used on an interpolating function with vector output [duplicate]

I am currently experiencing a problem when I try to use FindRoot with an interpolating function that outputs a vector. I have constructed a minimal example that ...
1
vote
1answer
123 views

What is most efficient way to convert system of equations to collection of functions?

I have the type of system M.x = b, where M is a known matrix and b is a known vector. M contains many parameters, call the entire parameter set 'a', so M => M[a]. I want to be able to efficiently ...
0
votes
0answers
73 views
5
votes
1answer
123 views

Solving an identity

I am trying to solve this identity using Mathematica: $$3 \sqrt{5 \sqrt[3]{37}-16}=\sqrt[3]{a}-\sqrt[3]{b}-c $$ I know that a, ...
1
vote
1answer
128 views

invert system of two parametric ODEs and plot results of do-loop

I can solve this system of parametric ODE (u is the parameter,while g,e and ...
-1
votes
1answer
93 views

Plotting the results of a system of equations

I believe this is a question of more list manipulation than plotting, but I hope you could help me. I solve numerically a system of equations of 3 variables, take only real solutions where one of the ...
1
vote
1answer
118 views

Perform FindRoots on Function Evaluation Containing RootSearch

I am using Ted Ersek's RootSearch function in Mathematica 9.0 (http://library.wolfram.com/infocenter/Demos/4482/) to create a function that I am using for graphing. ...
6
votes
4answers
303 views

FindInstance (and Solve, …) abysmally slow on a fully determined system of linear equations and inequalities: why?

I took a quick look for FindInstance and Solve-related questions but came up empty for the aspect that I am curious about. So ...
1
vote
1answer
117 views

How to do Inverse formulas/Rearrange formulas in Mathematica? [duplicate]

Hi am a student in chemical engineering and I have the necessity to rearrange formulas algebraically, for example ...
2
votes
1answer
113 views

Deriving least-squares equations in Mathematica

I define $Y = a + b*x + e$, and I want to find values for $a,b,$ by least squares, so I minimize $RSS = sum((Y_i - a - b*x_i)^2)$ I then take derivatives, ${d RSS \over da} = 0$ and ${d RSS \over db} ...
0
votes
3answers
253 views

How to find integer solutions?

Following is the equation: Need to solve for integer values of x,y when a,b lies between -1000 and 1000. Problem is to find the number of integer values of pair (x,y) that satisfy it.
12
votes
1answer
634 views

Proving inequalities with Mathematica

Question summary: I would like to learn some tips and tricks on how to prove inequalities with Mathematica. I'm studying various inequalities in triangle that have the form $R+ar + bs\geq 0$, where ...
5
votes
1answer
184 views

How to substitute the following conditions into an expression?

I have an expression: $p=a\;b\; x + b^2\; y + a\;c\; z$. I want to substitute $a\;b=1$, $b^2 = 2$ and $a\;c = 4$ to obtain $p = x + 2y + 4z$. How can I tell Mathematica to do that? I dont know how to ...
2
votes
1answer
555 views

How could I define a function as the solution of equations in Mathematica?

I have posed a specific question yesterday but it may be too trivial to answer. I think the question could be asked in a more general way so it is easier to answer. Then I could solve the original ...
1
vote
4answers
195 views

How do I create a list of 25 random quadratic equations in the form ax^2+bx+c?

My teacher suggests using the RandomInteger command along with the Factor command, but I cannot figure out the syntax. A, b, and c need to be non zero integers between -10 and 10.
0
votes
6answers
351 views

Can someone help me solve this x*y*z=180

I have one question I've been trying for a while but I can't get the result for my equation.. So I've been trying hard but I can calculate only by hand but the problem is that I am afraid to miss any ...
0
votes
1answer
97 views

How to get a solution for the following equation?

When I try to solve this equation using Mathematica: Solve[Exp[b*x]-c*(x^2)-a*x-1 == 0, x] /. {a -> 6.336, b -> 8, c -> 32} I don't get any result and ...
0
votes
0answers
23 views

Jacobian matrix formation from polynomial expressions [duplicate]

I want to find the jacobian matrix for 3 polynomial expression with 3 variables.. the polynomial expressions have the degree of 8.how to form it.?
-1
votes
1answer
94 views

Solve set of non linear differential equations [closed]

I have set of differential equations. For example, I took two equations and tried to solve them as below. I am not getting any results. Please help me to figure it out the mistake. And I wonder if I ...
1
vote
1answer
92 views

Solve equations for all values of variables, rejecting certain types of solution

I have an expression, expr, containing 3 variables, 4 coefficients and 2 non-zero generic constants. I want to solve for the 4 coefficients such that the equation ...
0
votes
0answers
44 views

Using Assumptions with Solve [duplicate]

Suppose i have a function defined as follows - f[x_] := E^-x - E^(-2 x); I want to find the max/min hence need to find when f'[x]==0. So i tried the following - ...
4
votes
2answers
722 views

Can mathematica solve this equation?

I have the following Mathematica code to solve an equation coming from isoparameteric finite element for quadratic tetrahedron element. I need to get the iteroplation fast and accurate. I only find ...
5
votes
2answers
348 views

Reducing exponential inequalities fails

I am quite stumped by this problem : Reduce[ N^(x-y) <1 && N > 0 , x, Reals] gives the expected result ...
10
votes
2answers
507 views

Finding all possible solutions to a math mind game

In the example below the letters shall be replaced by numbers. The numbers are from 1 to 9, and each letter has the same number ...
4
votes
2answers
169 views

Reduce with Integer domain, but receive a rational solution

I want to find the integer values $k$ so that D[f[x], x] has integer solutions. I tried ...
0
votes
1answer
40 views

Error when solving equations constructed with Table [duplicate]

I have a couple of questions about the problem I am trying to solve ...