# Tagged Questions

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

0answers
91 views

### Find all the integer numbers $a$, $b$, $c$, $d$, $e$, $f$, $k$ to this equation have three integer different solutions?

How to choose all integer numbers $a$, $b$, $c$, $d$, $e$, $f$, $k$ belongs to interval $[-20,20]$ to the equation $$\sqrt[3]{a x + b} +\sqrt[3]{c x + d} + \sqrt[3]{e x + f} =k$$ has three integer ...
1answer
152 views

### Efficient way to solve equal sums $x_1^k+x_2^k+\dots+x_5^k=y_1^k+y_2^k+\dots+y_5^k$ with Mathematica?

I need to solve the system of equations, call it $S_1$, in the integers $$x_1x_2x_3x_4x_5 = y_1y_2y_3y_4y_5$$ $$x_1^k+x_2^k+\dots+x_5^k=y_1^k+y_2^k+\dots+y_5^k,\;\; k= 2,4,6$$ I used a very ...
0answers
51 views

### Bounds on random number

I have a Markov Chain Monte Carlo code that uses a chi squared function to fit some data. I am running into an issue now with getting unrealistic values for some of the free parameters in the code. ...
1answer
149 views

### The Orbit and Perigee of the Flamsteed comet

Historical context This year we have the 330-th anniversary of the Battle of Vienna - one of the great formative events of European history, it took place on September 12, 1683. Kara Mustafa, Grand ...
0answers
34 views

### Evaluating the different calculations

I am a new user. I wonder that either there is possible to evalute different calculations at the same time in Mathematica or not? Can i share the kernels for different calculation at same time?
0answers
60 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 ...
1answer
88 views

### Solving for variables in a series of nonlinear equations [closed]

I have a nonlinear expression in five variables. I want to use Mathematica to solve for three of the variables. I have a series of points giving values of x an y and I am trying to solve for a,b, and ...
0answers
66 views

### draw a graph of a polynomial function with variables in the denominator [closed]

I have an equation f(u,z1,z2)=0, which is a long and complicated polynomial function with u in denominator. ...
0answers
57 views

### Rearrange this equation so x is the subject [closed]

I have this equation: y = 0.1x^3-0.2x^2 + 0.4x + 100 Can someone rearrange this equation so x is the subject. Thanks.
0answers
42 views

### Collect and factor equations with certain terms

Collect user defined terms from a symbolic algebraic expression ...
0answers
61 views

### Maximum root by using FindRoot [closed]

Assume f[x_, y_,z_] := Block[{A}, FindRoot[Abs[r[x, y, z]] - w[z] + 1 == 0, {A, 100}]] where ...
2answers
118 views

### find where 3 inequalities are simultaneously greater than zero

I have 3 functions, f11[l], f12[l] and f13[l], and I would like to know for which values of l these 3 functions are greater than zero. How do I do it analytically or numerically or graphically in ...
1answer
79 views

### Prandtl-Meyer function

I'm trying to solve for Mach number based on the given Prandtl-Meyer function, however I keep getting odd error. Here is my code: ...
0answers
80 views

### I can't solve this set of equations

I am having trouble solving a set of equations in mathematica. I do not get any errors, but i don't get any answers as well. I have some restrictions on my parameters and variables in the equations ...
3answers
192 views

### Solve for the intersection point of 3 surfaces

Basically, I have three 2-torus (tilted) in 3-dimensional Euclidean space. They are expressed by parametric equations: ...
2answers
97 views

### Count and plot the number of solutions in an interval

I have equations depending on one or more parameters and I want to find and plot the regions in the parameters space in which there are a specific number of solutions. For definiteness let's ...
1answer
167 views

### solving a cubic equation

I need to find the minimum $r$ and the maximum $k$ of the following cubic equation for which there does not exist three distinct real roots. $rx^3-rkx^2+(r+k)x-rk=0$. Is it possible to find such $r$ ...
0answers
6 views

### Identify the curve from the sample points [migrated]

I am writing a script which will identify the patterns drawn on the touch-pad of the laptop. I have generated all the points where user moved his finger over the touch-pad using synclient. Now i ...
0answers
62 views

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1answer
43 views

### How can I solve this system with Mathematica? [closed]

Systems with 3 equations and 3 unknowns ... The unknowns are {p,q,j} ...
1answer
119 views

### How can I solve this nonlinear system with 3 equations and 3 unknown? [closed]

I have this system with 3 equations and 3 unknowns: ...
0answers
55 views

### Is there an error in this simultaneous equation? [closed]

I am a novice to Mathematica. Just curious to know why this simultaneous equations isn't working: ...
0answers
76 views

### Solve equations real and imaginary part separately

For my system of equations, the procedure described in Solving complex equations of using Reduce works no more. How can I separate the real and imaginary part of ...
1answer
59 views

### Error/warning when using NSolve for simple equation

I am using NSolve to solve an equation, as shown here: ...
1answer
56 views

### Finding the root of a nested function with small values

I have reduced an error in my program to this line of code: FindRoot[Nest[# (1 - #) k &, 1/2, 2^4] - 1/2, {k, 3.5}] It works for $2^1, 2^2, 2^3, 2^4,$ but ...
1answer
128 views

### Symbolic Simulations

I have 9 nonlinear equations and 10 unknowns. It is not possible to obtain a numeric solution but I do get a parametric solution. It is useful in my case because I want to observe how parameters (p1, ...
0answers
112 views

### FindRoot gives a wrong solution which obviously should not be there

I got stuck on FindRoot and I didn't see any similar problem posted, so let me explain what I am trying to do and what problem I meet here. I try to find roots of a particular function, which in the ...
0answers
55 views

### Exposing a variable [closed]

This is the basic equation \[Sigma][T]=E^((-20.7302 + 0.0147986 T) x) (625.646 - 3.50008 T) x^( 1.03651 - 0.000739932 T) Then there are commands: ...
0answers
108 views

### Nest for large value of n

I am working on a problem to find the Feigenbaum constant. In this problem I have to get $f^{2^n}(1/2)$ with $f(x) = kx(1-x)$. I use Nest to get $f^{2^n}(1/2)$ but ...
1answer
81 views

### Solving a system of equations

Mathematica doesn't want to solve my exact system with 3 equations and 3 variables. ...
0answers
140 views

### Creating and using an explicit piecewise function in a convenient way

I have a set of data points that define a function in the form curvePts = {data1,data2,...} where ...
1answer
128 views

### How to find the smallest positive root [closed]

My problem is : ...
1answer
87 views

### A basic problem with Solve

I have this equation: 4b*Cos[2t]-4a*Sin[2t]==4Cos[2t]+8Sin[2t] Which I would like to solve. Without using mathematica, you can pretty easily see that a = -2 and ...
2answers
202 views

### Mathematica does not understand (R^3)^(1/3) is the same as R [closed]

In the output from a calculation in mathematica stands a/((R^3*c)^(1/3)), with c and a ...
0answers
73 views

### Conditional statements in intial conditions?

This is potentially a daft question, but I thought I'd ask it; I have some material free to diffuse in a boundary between rn and ro; I've been able to get it working nicely for neumann type boundary ...
0answers
72 views

### Simultaneous Equation Solving Under Nonnegative and Bounding Conditions

I have nonlinear equations to solve parametrically; ...
1answer
121 views

### solution of differential equation

I have the following code that gives you a phase portrait of a 2d system and I can't understand what means the 3rd and 4th line (sol1 and sol2). ...
1answer
47 views

### Define variable relationships and dynamically update variables

I would like to define a relationship between 3 variables first and then later when I have filled two of the variables with a number, I would like to extract the value of the last value. For example: ...
1answer
36 views

### How to delete duplicate solutions of this system of equations?

I want to find vertices (has integer coordinates) of the triangle $ABC$ with the centorid is $G(1,1)$ and orthocenter is $H(3,3)$. I tried ...
1answer
114 views

### Solving Intervals

In a recent question I posed, it was noted that by design, Sqrt[ blah] only returns the positive branch, even though we might want to obtain all possible symbolic solutions. So, taking care to avoid ...
1answer
87 views

### Why is FindInstance failing when I relax a set of constraints?

I'm attempting to use FindInstance to generate coordinate sets for plausible triangles with edge length distance constraints. E.g.: ...
1answer
139 views

### How to solve this equation with integers as a solution?

I want to solve the equation $$x^y + y = y^x + x$$ with $x$, $y$ are integer numbers. I tried Solve[x^y + y == y^x + x, {x, y}, Integers] How to solve the ...
0answers
47 views

### DSolve::overdet for system of linear PDEs

I would like to resolve symbolically the following equation: ...
2answers
128 views

### Using RSolve correctly

I am having problems persuading Mathematica to solve even the simplest recurrence relations. As an example, how would you do the following? ...
0answers
72 views

### Defining and Solving Systems of Equations Using Matrix Tables

I've defined a system of equations, but I been unable to get Mathematica to solve for the individual variables created by matrix tables. ...
2answers
108 views

### Using FindRoot with an interpolating function

This question bears resemblance to a few other questions on mathematica.SE about finding points of intersection of crossing curves. I know that the guidebook of numerics has an entry about the whole ...
3answers
199 views

### Solving a system of equations with conditions related to the number of solutions

The equation below describes a conic with oblique axis: $$9 + 22 x + 9 x^2 + 46 y + 24 x y + 16 y^2=0$$ It is a parabola, as the coefficients in $x^2$, $y^2$, $xy$ form a perfect square. To find the ...
1answer
73 views

### Find point at which equation stops having roots (if it exists)

I am interested in the roots of this function: f[M_, b_] := 1 - (2 M Gamma[2, 0, (1/M + b M)/Sqrt[b]])/(1/M + b M) for fixed values of b. In particular I want ...
0answers
50 views

### Finding all roots of the system of two complex equations

I need to find all roots for the system of two complex equations. Obviously I can rewrite them as 4 real however problem remains. I have looked through routines connected with using ContourPlot ...
1answer
63 views

### Plotting query - same values on Y-axis / viewing data

I'm new to Mathematica, and have numerically solved two similar functions with the following code; ...
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