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

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1
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1answer
156 views

Unable to solve a set of equations with Solve

I'm trying to solve the following equation using Mathematica 9.0.1.0 : ...
0
votes
1answer
60 views

How to write a variable in terms of the other [duplicate]

I have an equation that defines a variable like y=4x+a. I had another equation, z=x+2+4, I would like to know if there is a way in Mathematica to get an expression in which z= a*y+C, in which a and C ...
0
votes
1answer
56 views

Why Solve won't work for user-defined function, used for system solving? [closed]

I have a list of x-es, that I transform into a list of tx-es. Also tao is my user-defined function that I don't know the parameters of, but I do know the values I get when I put the tx-es in it. And ...
2
votes
1answer
69 views

Simplify equation using conditions/inequalities

If I have an equation like f[x](1 + a)==0 I'd like to be able to tell Mathematica that 1+a doesn't vanish in general, and get back ...
0
votes
3answers
97 views

Partial products in prime steps [duplicate]

I am trying to find out partial products going up in prime steps for Euler's product formula $$\prod_{p} \frac{1}{1-p^{-s}}$$ Trying things like ...
1
vote
2answers
163 views

Find the centre of FindGeometricTransform

I'm interested in using Solve[] to find the centre point of rotation (as an $x,y,z$ coordinate point) and axis of rotation (as a vector) from a ...
0
votes
1answer
66 views

Solving polynomial equations takes infinit time

I need to solve an polynimial equation, but when i try to use Solve or NSolve in mathematica, its cant find the solution in appropriate time (i interrupted calculation after 5 hour left). The ...
0
votes
3answers
130 views

Solving algebraic equations

How may I make n and k in terms of x and y in this ...
4
votes
2answers
160 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
148 views

Reduce Cannot Solve Complicated Function

As per the answer to this question: SolveAlways rejects inequality, I tried the following commands: ...
0
votes
1answer
64 views

SolveAlways rejects inequality

I have two functions of x, f and g. f[x] = g[x] + 2, ...
1
vote
3answers
172 views

Plot a table of ranges

I have table with values like: t = {1.234 <= a <= 2.345, 3.42 <= a <= 5.67, ...} and I want to plot this table, the ...
3
votes
2answers
144 views

Solve-ing with initially unassigned parameters and Solve-ing using their numerical values produces different results

I am trying to solve an equation using the following piece of code: ...
1
vote
2answers
187 views

Equating coefficients in a non-power-series equation

How can I use Mathematica to equate coefficients in a non-power-series equation? For example, I would like to take an equation like the following: ...
2
votes
1answer
254 views

Speeding up solving a system of simultaneous equations

I am trying to solve the following system of equations. Solve takes a very long time to solve the following system of equations. Is there any way to speed it up? ...
2
votes
1answer
86 views

Declaration of variables in large Linear Programming model with NMaximize

I want to solve a large LP problem using NMaximize. This is a small instance of my bigger problem: $$max \sum^{4}_{t=1}(\sum^{4}_{c=1} V_{c}*f_{c,t})\\ s.t\quad ...
0
votes
1answer
74 views

Reduce[] giving incorrect result for equation over $\mathbb{Z}^4$

This is partially in response to a question I posted earlier, although the problem in this case appears to be distinct from the problem there, so I am temporarily filing this as a separate question. ...
1
vote
0answers
92 views

Solve[] unexpectedly giving empty solution sets for extremely large problems

I was calculating the set of lattice vectors in $\mathbb{Z}^4$ which have taxicab norm $r$. For example, executing ...
1
vote
1answer
140 views

I got wrong answers when solving an equation

I have this expression: ...
3
votes
1answer
143 views

Faster Solve for Fermat 4n+1 conjecture

Assuming that Fermat 4n+1 conjecture (each prime of the form 4n+1 is the sum of two squares) is true then I like to solve the ...
1
vote
1answer
108 views

Decomposing a diagonal positive real matrix

I would like to 'decompose' a diagonal positive real matrix $E$ of rank $D$ onto $\sum_{i=1}^{D}c(i)N^i$: $$E = \left( \begin{array}{ccc} 0 & & & \\ & a & & \\ ...
0
votes
1answer
144 views

How to enter and solve this equation in finite fields?

Is there a way in Mathematica 9 to enter and solve the following equation $p(x) = r^x$ where $p(x)$ is a polynomial whose coefficients are drawn from a finite field, and $r$ is a primitive root of ...
2
votes
2answers
94 views

Quadratic Equations mod p^k

As part of a larger program, I need to solve $A x^2+B x+C \equiv 0 \mod p^k$ for prime $p$. Right now I'm doing this by calling ...
1
vote
0answers
64 views

No response from DSolve

Using optimal control theory, I am trying to find the optimal paths of d and k such that they will maximize profit as given by lc: ...
1
vote
1answer
92 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. ...
2
votes
3answers
138 views

Extracting coefficients from g=a*x+b*y+c*x*y

I have a Response Surface Equation (RSE) that I'm trying to extract coefficients from. It has a form similar to: g = a*x + b*y + c*x*y; I want to be able to ...
1
vote
1answer
73 views

Asymptotics of sum of binomials

I would like to find the asymptotics of Sum[Binomial[n,i]*1/i^((n+1)/2),{i,1,n}] I saw Find asymptotics of Sum[2^i*Binomial[n-i-1,2*n/3-1],{i,0,n/3}] but I ...
1
vote
1answer
120 views

Problem to solve an integral equation [closed]

I am new to Mathematica. I am trying to numerically solve for C in the following equation: $\begin{equation} \begin{array}{lcl} -\int_0^\infty (5000000+100000 x+ C)^{-1} ...
2
votes
1answer
76 views

Solving Complex Equation Over Reals

I want to solve the equation $\frac{abi}{a+bi}=4-2i$, where $a$ and $b$ are real numbers. I know from hand-solving the answer is $a=5$, $b=-10$. How do I get Mathematica to tell me this? I tried: ...
2
votes
1answer
171 views

Resonance Curve using NDSolve

I am trying to make a resonance curve like this one below, using NDSolve. I tried to use code as below. Basically I try to hold solution for a w (driving frequency value) using NumericQ and then ...
0
votes
0answers
62 views

Algebraic condition from a non linear equation

I have got a system of equations which look like this: $\theta_{1}^{2}e^{\phi_{1}\cos(\Omega z)}\tilde{w}\cos^{2}(\theta_{1}\sin\Omega z)\sin^{2}\Omega z+\frac{1-\lambda\cos(2\theta_{1}\sin\Omega ...
0
votes
0answers
97 views

Second-order DSolve overdetermined with only 2 boundary conditions

I was going through some circuit analysis problem and came up with a second-order differential equation, which I decided to solve with Mathematica: $$ L\frac{\mathrm{d}^{2} I}{\mathrm{d}t^{2}} + ...
0
votes
0answers
75 views

Issue with NDSolve

This could be a stupid issue, but I have been checking for ages. I cannot solve this apparently innocuous system of PDEs: ...
0
votes
1answer
81 views

Failure message from Reduce

I am getting the message Reduce::nsmet: This system cannot be solved with the methods available to Reduce. while trying to solve the following equation: ...
5
votes
1answer
280 views

Calculate max value

Update Using ...
0
votes
0answers
43 views

Store results of inequality [duplicate]

I eveluated some values using Reduce commend and I store them in a Table ...
2
votes
1answer
106 views

Solving problems with the floor function

I've got the following problem: If I want to calculate the following equation, ...
2
votes
2answers
141 views

Plotting double inequality only for integer values

RegionPlot is plotting for all values. And using ListPlot I can only evaluate one inequality. How can I plot this type of ...
2
votes
2answers
164 views

Solve the system of equalities and inequalities

I have a system of expressions, in which each expression is an equality or inequality expression of the following form: Var = Var1 + Var2 Var $\odot$ number Var $\odot$ Var1 $\odot$ = $\leq | \geq | ...
1
vote
3answers
111 views

Discrete inequality plotting

I have an equation like this: $${20 \choose k}\cdot \sum_{i=0}^k {k \choose i}\cdot i \leq 1+f$$. I want to plot this inequality as the dependency between k and ...
0
votes
3answers
88 views

Reduce of a table [duplicate]

I have a table for example: t = Table[k,{k,5}] which returns {1,2,3,4,5} and for every element in this table I want to check ...
0
votes
0answers
73 views

Assigning the answer of Solve to a variable [duplicate]

If I enter Solve[(x-2)(x+2)==0,x] then the answer comes up as {{x -> 2}, {x -> -2}} I want to make two variables ...
3
votes
0answers
126 views

How to get vertices of a polytope given by equalities and inequalities?

I have a polytope given by some equalities and inequalities, how can I get all the vertices of the polytope? If there's a way to deal with the one given by inequalities only, how can I reduce the ...
1
vote
1answer
122 views

Solve returns a wrong answer

I'm afraid the following is rather localized questions, but I don't know how to simplify and generalize it. I have the following two points (in the real plane): ...
3
votes
3answers
215 views

How can I calculate a combination of limit and sum?

How can I solve the above problem? I enter it as: Limit[Sum[Sqrt[1 + i^2/n^2]/n, {i, n}], n -> Infinity] but this is not working:
1
vote
1answer
104 views

NSolve with numerical function

I would like to solve numerically an equation which involves a numerical function constructed by fitting some data: ...
0
votes
3answers
256 views

Solving a differential equation with mixed conditions using DSolve

I want to solve a differential equation $$ \frac{d}{dx}\left(k_0 \left(\frac{T(x)}{T_0}\right)^n \frac{dT(x)}{dx}\right)=0,$$ with boundary conditions: $T(l)=T_0$, $\;T'(0)=-\frac{q_0}{k_0 ...
0
votes
0answers
67 views

Reduce - Most efficient expression - Using FullSimplify

I am trying to solve complicated inequalities using Reduce, in order to determine whether certain mixed equilibria in game theory are stable. My first question ...
2
votes
2answers
162 views

Check if integer has even number of digits

I want to check if a number has an even or odd number of digits. 10 would be even because it has 2 digits 300 would be odd ...