New answers tagged equation-solving
3
votes
Accepted
Extract boundary points of an interpolating function obtained by NDSolve
We can use "Domain" to extract the values.
{rmin, rmax} = (h /. sol[[1]])["Domain"][[1]];
rmin
rmax
- 63.3k
2
votes
Accepted
Plotting an integral with solving for a specific constant
As an example, we take a simple function that we can integrate analytically:
f[t_] = t + 2;
Integrate analytically:
...
- 45.9k
5
votes
Accepted
Strange behavior of GroebnerBasis
Obviously MMA consider n as a variable. You can see this by writing:
GroebnerBasis[1/(n (n - 1)) + x, {x, n}]
what is the same as your result. To circumvent this, ...
- 47.1k
0
votes
How to modify the order of symbols to make the result more logical
The warning by @Bill in a comment about *Form functions is well made.
The following works, but it appears that PolymonialForm ...
- 15.5k
1
vote
Solution of a sixth degree polynomial
It is advantageous to solve the expression for x first and introduce new parameters a -> \[Alpha] M, r -> \[Rho] M:
...
- 49.1k
2
votes
How to modify the order of symbols to make the result more logical
The function "rearrange"
The function rearrange[expr,listOfFinalPositions] rewrites a sum in the order prescribed by the list entitled "...
- 38.7k
0
votes
FindRoot with input as a list
Your equations are simple enough that you can use Solve:
Solve[{eq1==0, eq2==0, eq3==0}, {a, b, d}]
{{a -> -60, b -> (k (...
- 130k
1
vote
1
vote
2
votes
How can I choose the integer numbers a, b, c, d, t so that the equation $\sqrt{a x^2+b x+c}=d x+t$ has two integer solutions?
No need to use FindInstance. In fact you can generate all possible equations with prescribed roots r1 and ...
- 9,653
2
votes
3
votes
Accepted
Getting all solutions to an equation on condition the variables are either 0 or 1
FWIW this can be solved by brute force:
e.g.
b = Tuples[{0, 1}, 3];
t = Tuples[{0, 1}, 8];
sol[s_] := Select[t, Mod[# . b, 2] == s &]
Solutions can be ...
4
votes
Getting all solutions to an equation on condition the variables are either 0 or 1
An equivalent version to user64494's answer is the following:
...
- 130k
3
votes
Getting all solutions to an equation on condition the variables are either 0 or 1
This can be done as follows.
...
- 24k
1
vote
Multiple solutions from NSolve
With the OP's sol, we can gather the similar solutions together, find their mean, and if desired, polish them up with FindRoot:
<...
- 773
4
votes
Accepted
How to solve this integral equation numerically?
Although the general problem in the question probably requires the methods referenced by flinty in 285076, the specific problem contained in the question's code, ...
- 60.7k
5
votes
Accepted
Numerical solving diffusion equation in spherical coordinates
Change your boundary conditions to DirichletConditions
...
- 49.1k
1
vote
First order differential equation with two conditions
To long for a comment!
You might check your expected solutions directly. Examplary for the first one
...
- 49.1k
0
votes
Accepted
Problems with Solve. Only works for specific parameters. Solve function do not "start"
Your claim "the programm [program] do [does] not start the Solve function process" is not true: the returned inputs mean the Solve cannot solve those and ...
- 24k
0
votes
Solving A System of Two Implicit Equations
An alternative approach is to use FindRoot or FindMinimum without constructing an ...
- 60.7k
3
votes
Accepted
Selecting Solve results according to conditions
You can add those conditions in Solve, but you also need to specify eg that $a>0$:
...
- 65.8k
4
votes
Selecting Solve results according to conditions
There could be shorter way. How about
f[x_, y_] := L x y;
g[x_, y_] := x^2 + y^2 - a;
res = SolveValues[D[f[x, y] + λ g[x, y], {{x, y, λ}}] == 0, {x, y}, λ]
and ...
- 137k
4
votes
Accepted
4
votes
Accepted
0
votes
Can a redundant condition be removed from a solution?
Simply remove Reals from your code if you do not want the condition.
Solve[{(p-x)^2 + (q-y)^2==d, p/q==t}, {p,q}]
$$\left\{\...
- 9,653
1
vote
Accepted
Can a redundant condition be removed from a solution?
The simplest way, no pun intended, to remove your condition, tell Simplify it is true.
...
- 11.7k
0
votes
Accepted
How can i create an equation with a sum?
Have you checked on-line help? Anyway, I would make a list of the variables, and use that. Something like:
...
- 1,059
3
votes
2
votes
`Reduce` is running forever
Designate the sixteen inequalities given in the question as ineq. The corresponding variables are
...
- 60.7k
4
votes
Accepted
3
votes
Multiple solutions from NSolve
For parametric research it could be better to use FindRoot as follows
...
- 41.8k
1
vote
Multiple solutions from NSolve
Setting WorkingPrecision->20, it then takes 85 sec. and gives only 3 solutions, although it gives a warning that the input is less precise than working precision:
...
- 47.1k
8
votes
4
votes
Accepted
0
votes
Solving a non-algebraic equation at the symbolic level
As @Artes guessed, Mathematica 13.3.1 on Windows 10 can demonstrate both solutions are equal. For example,
...
- 24k
1
vote
Accepted
2
votes
Solving Nonlinear Algebraic Equation
It solves it fast if you use Reals. Also you really should use Exact input with Solve
...
- 137k
1
vote
1
vote
Accepted
Newton-Raphson Method Errors
The built in function FindRoot can solve your equations. I believe it uses Newton's method by default, though you can choose other options. For your equations, I found singularities were occurring ...
- 1,036
5
votes
Real zeros of complex function
Your function $\xi(k,B)$ does not depend on $B$ directly but only on $\cos(B)$, in a simple way. You can solve $\xi=0$ for $\cos(B)$ and thus find $\cos(B)$ as a function of $k$.
...
- 45.9k
3
votes
0
votes
Limit the number of the results returned by Solve to some specific number
A really simple way to get less solutions is to make your constraints tighter. Here I change the first constraint to be 10<=x[1]<=10 instead of ...
- 3,453
0
votes
Accepted
Limit the number of the results returned by Solve to some specific number
One of the ways is as follows.
...
- 24k
2
votes
How to solve this integro-differential equation in Mathematica?
Your equation is separable and can be solved analitically. If you define
$$c(x,t)=c_1(x)c_2(t)$$
and substitute back into your equation, you see you obtain the two equations:
$$c_2^\prime(t)=L\,c_2(t)$...
- 6,557
1
vote
How to solve this integro-differential equation in Mathematica?
Mathematica can't solve your integral equation, DSolve only returns a simplified form I think:
...
- 49.1k
2
votes
Solve[] isn't producing a correct result
To long for a comment
NSolve evaluates all zeros for given parameter
parameters (from @Larson's GeoGebra picture )
...
- 49.1k
1
vote
Is there a way to divide associations by key?
a = <|A -> 2.02015, B -> 1.98025|>;
b = <|B -> 0.538000, A -> 0.462000|>;
In the above case it's simply
...
- 47.6k
4
votes
Solving system of first order PDEs
Update: Solution accuracy modestly improved and accuracy estimate appended.
The Finite Element Method used in the last section of the question approximates the PDEs by thousands of sparsely coupled ...
- 60.7k
4
votes
Finding poles of a function
Since V 13.0 we have FunctionPoles:"
From the documentation: "FunctionPoles returns a list of pairs {pole, multiplicity}."
...
- 47.6k
Top 50 recent answers are included