Questions on the analytic and numeric equation solving functions of Mathematica (Solve, Reduce, NSolve, FindRoot, DSolve, RSolve, etc.).
0
votes
1answer
157 views
Solve telling me all my solutions are zero
I'm trying to use Mathematica to solve a complicated system of equations. Here is a screenshot of the equations, and what Mathematica outputs.
The variables $v_i$ and $w_i$ act as constants in ...
3
votes
2answers
152 views
Eliminate several variables between five Conic_section equations
I want to eliminate x1, x2, y1, y2 between these 5 equations.
I tried
...
-1
votes
1answer
99 views
Solving an equation for asymptotic dependence of the solution on a coefficient
I have an equation I want to solve, so I entered the following into Mathematica.
(x^(17/6))/(a^(17/6)) - (x^2)/a -1 == 0
where I assume $a>>1$ and $x$ is ...
3
votes
2answers
174 views
How can I solve an equation with symbolic coefficients?
I want to try to solve the following
a x^(17/6) - b x^2 - 1 == 0
where a and b are ...
2
votes
2answers
199 views
Solving set of non-linear simultaneous equations gives PolynomialGCD::lgrexp error - what next?
I'm trying to solve a set of six simultaneous non-linear equations to get a numerical answer using NSolve:
...
0
votes
1answer
54 views
Create set of equations by replacing constant values
Say I have an equation:
eq = ax + by + c == 0
and I want to run NSolve on a set of equations of this form, for example:
...
0
votes
0answers
93 views
using FindRoot in for loop [closed]
I am fairly new to Mathematica so I am not really familiar with all the "kinks" in its syntax (a matlab lover).
I am trying to run this:
...
2
votes
3answers
261 views
Using DSolve to solve for x[t,parameter]
I'm trying to solve an ODE with two independent variables (a cannon firing from a cliff incorporating wind resistance dependent on velocity). I've tried the following for the x-component:
...
2
votes
2answers
85 views
Why can't FindInstance find a solution to this equation?
FindInstance[680 == 1/3 2^m (-1 + 4^v), {m, v}, Integers]
FindInstance seems to be unable to find the integer solution $ {m = ...
2
votes
0answers
106 views
Am I entering this 2-variable recurrence correctly?
I'm trying to solve this recurrence with two variables.
...
1
vote
1answer
322 views
Linear Solve with Modular Arithmetic
I am interested in using LinearSolve[m,b] which will find a solution to the equation $m.x=b$, where I am in mod 2 arithmetic. Is there any way to perform this ...
2
votes
1answer
108 views
How can I get the general term of this recurrence equations?
Following is the recurrence relation:
a[1] = 1;
a[n_] := a[n - a[n - 1]] + 1
Array[a, 28]
I tried to use RSolve, but it ...
2
votes
1answer
398 views
NSolve: Mathematica 9 issue
In Mathematica 8 the following expression evaluates and returns a result in terms of InverseFunction:
...
0
votes
0answers
182 views
Why does Mathematica fail to solve my equation?
I am trying to solve an equation using Mathematica, but I keep getting the
following error
Solve::nsmet: This system cannot be solved with the methods
available to Solve.
More importantly, ...
1
vote
1answer
96 views
Finding parameters for first positive root of solution to differential equation to be equal to a desired value
I have a differential equation with parameters. The objective is to vary the parameters such that the first positive root of the solution is equal to a desired value ...
0
votes
1answer
163 views
I can't get Compile to work
I've got some problems with my code, and I try to make it faster. Some of you suggested me to split my problem, and I'm here...
I post the same function with and without Compile.
This is a support ...
4
votes
2answers
133 views
How can I eliminate equivalent equations from a list?
I want to find the numbers $a$, $b$, $c$, $d$ of the plane $ax + by +cz +d = 0$ which make the distance from the point $M(1,2,3)$ to the plane equal to 2. I tried
...
1
vote
2answers
129 views
Is there a better way to get the eight points of intersection?
I want to get the eight points of intersection from the equations 2 Abs[x] + Abs[y] == 1 and Abs[x] + 2 Abs[y] == 1. To solve ...
5
votes
4answers
521 views
How to get exact roots of this polynomial?
The equation $$ 64x^7 -112x^5 -8x^4 +56x^3 +8x^2 -7x - 1 = 0 $$
has seven solutions $x = 1$, $x = -\dfrac{1}{2}$ and $x = \cos \dfrac{2n\pi}{11}$, where $n$ runs from $1$ to $5$. With ...
1
vote
1answer
338 views
Forcing FindRoot to return only real solutions
FindRoot documentation reports that if the Equation and the initial point are reals, the solutions are searched in the real domain.
However, in the following case I ...
5
votes
2answers
409 views
Can mathematica solve this equation?
I have the following Mathematica code to solve an equation comes from isoparameteric finite element for quadratic tetrahedron element. I need to get the iteroplation fast and accurate. I only find ...
0
votes
0answers
188 views
Vertices of the region defined by inequalities
I have a set of 8 inequalities in two variables $X$ and $Y$. In Mathematica, using the command Reduce I find the solution. The solution plotted with ...
2
votes
1answer
191 views
How can I solve an exponential inequality in Mathematica?
I would like to solve the equation:
A Exp[m t + s Sqrt[t] x - 1/2 s^2 t] >= K
with respect to x (which is in the exponent) ...
2
votes
1answer
114 views
What's the difference between the following two codes?
I have two codes to find the integer numbers $m$, $x$, $y$, $z$ in the system of equations.
First code
...
0
votes
1answer
113 views
0
votes
0answers
61 views
please help to me, Where is my mistake? [closed]
e = {{v, -37925.9}, {-37925.9, s}}
v = (37925.9 - 12.74 x)
s = (7585108 - 15029 x)
Solve [e == 0 , x ] please help to me, Where is my mistake?
0
votes
1answer
101 views
Manipulate[]'ing complex roots of an equation using a 2D slider [closed]
I want to make a demonstration of how the complex roots of a polynomial change when I alter the coefficients. Here is my attempt:
...
2
votes
1answer
94 views
Using NSolve on an equation that involves Mean and TruncatedDistribution
What I would like to do is create a mixture distribution that has a specified mean by varying one parameter in the distribution. To do this I've written the following code;
...
3
votes
0answers
69 views
Symbolic solution to ODE, pure InverseFunction not evaluated
I'm new to Mathematica and I don't understand why in the solution of the following ODE, the #1 in the pure function is not immediately replaced by the corresponding ...
0
votes
0answers
25 views
Handling “Solve was unable to solve the system with inexact coefficient” errors [duplicate]
Possible Duplicate:
How to get rid of warnings when using Solve on an equation with inexact coefficients?
I've been trying to calculate the following in Mathematica:
...
4
votes
1answer
242 views
How do I use RSolve to solve a system of recurrence relations?
I am trying to solve a system of recurrence relations as follows.
...
30
votes
2answers
719 views
What is the difference between Reduce and Solve?
Solve and Reduce both can be used for solving equations.
Just by operating them, I know there is little difference between them.
But, the only thing I know is that there is little difference, and I ...
3
votes
1answer
278 views
How to solve this equation with positive integers as a solutions?
This is a problem of United Kingdom Mathematical Olympiad. Find all triples $(x,y,z)$ of positive integers such that
$$\biggl(1+\dfrac{1}{x}\biggr)\cdot \biggl(1+\dfrac{1}{y}\biggr)\cdot ...
5
votes
4answers
512 views
How to find the sum all even numbers of this sequence?
I have a sequence $(u_{n})$
$$u_1= 1, \quad u_2 = 2, \quad u_3 = 3, \quad u_{n}= -u_{n-3} + 3u _{n-2} +2 u_{n-1}, \quad \forall n \geqslant 4.$$
I want to list the first $20$ terms of this sequence ...
4
votes
2answers
256 views
How do I solve this equation?
I want to solve the equation $$ f(f(-1)) = \sqrt{2} + g(f(2)), $$
where $$f(x) = \dfrac{a}{x^2} - 3x + 2, \quad g(x) = a\cdot \sin 2x$$
$a$ is unknown. The solution is $a \approx{-5.81}$. I tried
...
3
votes
1answer
444 views
Solving an Integral equation
I would like to solve the equation
$$\frac{2}{p}\int_0^1((1-u)^{1-p}+u^{1-p})^{\frac{1}{p}}\text{d}u=42$$ for p numerically.
I tried
...
0
votes
1answer
137 views
How to express endogenous variables in terms of exogenous variables?
I have 11 endogenous variables (RD, NR, WR, Q, NQ, R, L, W, NU, C1, C2) and two exogenous variables (EE, K).
I'm trying to find $RD = f(EE, K),\, NR = f(EE, K),\, ...,\, C2 = f(EE, K)$.
Hence, I ...
2
votes
1answer
297 views
'not a valid variable' error when trying to solve 13 equations with 13 variables
I want to solve 13 variables by 13 equations. And here is my program:
...
6
votes
3answers
573 views
Find all roots of an interpolating function (solution to a differential equation)
I'm trying to find all the roots of the solution to a differential equation.
Using NSolve or Reduce I don't get the roots, so I'm using an iterative method which I found in physicsforums.com.
This ...
2
votes
0answers
138 views
FindRoot - Speed and errors
I am using FindRoot[] to solve a complicated equation. It seems I get the correct answer even though I get errors about an ...
3
votes
3answers
1k views
How to get rid of warnings when using Solve on an equation with inexact coefficients?
When I solve this equation in Mathematica 8, I can get the right answer, but with some uncomfortable warnings.
Equation:
...
3
votes
3answers
302 views
Solving Integrals
Here's a problem that I don't understand.
f[x_] := Exp[Cos[3*x]]
g[x_] := (1/3)*x^3 - x^2 + 2
When I try to find the limit:
...
2
votes
0answers
83 views
Why cant Mathematica solve this equation? [duplicate]
Possible Duplicate:
Can Reduce *really* not solve for x here?
Why cant Mathematica solve this equation?
...
1
vote
1answer
102 views
How to extract Solve results as variables [duplicate]
Possible Duplicate:
Assign the results from a Solve to variable(s)
In the following example:
...
-3
votes
1answer
378 views
How can Mathematica solve this set of differential equations? [closed]
I'm trying to solve this set of non linear differential equations, but apparently it won't solve. I really tried all the tweaks I could think of. Still no progress... So now I turn to you, can you ...
4
votes
2answers
174 views
How to solve this trigonometric system of equations numerically?
How can the following trigonometric system of equations be solved numerically?
...
0
votes
1answer
112 views
Solve not satisfying simple boundary conditions
I am trying to solve the following equations for the coefficients c1 and c2.
...
1
vote
1answer
78 views
How to get a solution involving logs in the right form?
How do I get
Solve[(1/9)^(r/2) == 1/n , r]
to give me
Log[n]/Log[3]
and not
...
3
votes
1answer
117 views
Using external variable as a variable inside WhenEvent & NDSolve
I'm trying to use the new WhenEvent functionality of NDSolve in Mathematica 9, in order to perform an action when a variable in the system reaches a certain value. I would like this variable to come ...
2
votes
0answers
173 views
Numerically/Analytically Solving a System of Equations
I have $6$ functions $f_i(x,y,z)$, $(i = 1, \ldots, 6)$ in three variables $x,y,z$, and I would like to find a simultaneous instance of these variables, say $(x_0, y_0, z_0)$, such that $f_i(x_0, y_0, ...
