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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2answers
506 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: ...
1
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1answer
86 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....
0
votes
0answers
198 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
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1answer
2k views

Why Mathematica can't solve this? NSolve or Solve

I want solution of x and y which should be positive real numbers ...
2
votes
1answer
737 views

2d heat conduction equation: Boundary and initial conditions are inconsistent

I have the following code for a 2d heat c equation: ...
0
votes
1answer
87 views

Solve equation with two different sets of replacement rules

I want to solve eqn for c0 in the following code. I want to do it with both replacement rules. I realize I could just use solve ...
0
votes
1answer
317 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, {ub,...
3
votes
1answer
143 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 ...
3
votes
1answer
2k views

Why is Solve returning an empty list?

I evaluate ...
0
votes
1answer
138 views

2 Equations continuous at a point

I want to get continuous point between two equations. My equations are: ...
2
votes
1answer
130 views

Visualizing how the zeros for this function change as its input parameter changes?

I'm trying to explore how the zeros of a certain parameterized function change as its parameter changes. ...
0
votes
0answers
37 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 ...
2
votes
1answer
681 views

Solve[Tan[theta] == (b*Sin[t])/(a*Cos[t]), theta] breaks when “Reals” is added?

Mathematica solves this equation fine: Solve[ Tan[theta] == (b*Sin[t])/(a*Cos[t]), theta] // InputForm ...
0
votes
1answer
3k 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 ...
4
votes
2answers
255 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
0answers
33 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
250 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 ...
5
votes
1answer
155 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
0answers
169 views

Calculating derivatives of roots of equation

I am interested in calculating how the roots of an equation change as one of the variables does, when the equation is evaluated numerically rather than symbolically. I have edited this code to be ...
-1
votes
1answer
164 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
180 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
vote
1answer
385 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 ...
1
vote
3answers
6k 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.
2
votes
1answer
186 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} ...
22
votes
6answers
7k views

Finding the intersection of a curve with an interpolation function

There are no issues trying to find the intersection points of two defined curves. ...
1
vote
2answers
171 views

Symbolic solution of system

everyone! I am sorry, but I am an abcolute novice of Mathematica (to be more precise this is my first day of using it) and even after surfing the web and all documents I am not able to solve the ...
1
vote
0answers
234 views

Invert a transcendental function

I have tried Reduce and Solve in Mathematica, as well as have a long list of tries in Maple, but cannot seem to get anywhere ...
1
vote
4answers
490 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.
7
votes
1answer
774 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 ...
0
votes
2answers
364 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 ...
1
vote
1answer
185 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 ...
6
votes
5answers
850 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 ...
6
votes
4answers
895 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 ...
3
votes
3answers
253 views

Simultaneous equations

I am trying to solve two simultaneous equations that are claimed to have 145 solutions but I believe they have 143, I want to check I am right before sending an email to my professor. Mathematica is ...
0
votes
1answer
134 views

Error when solving equations constructed with Table [duplicate]

I have a couple of questions about the problem I am trying to solve ...
1
vote
1answer
2k views

Green's Function in Mathematica

The equation I am trying to solve is: $$q \, T_1''(x)-T_1(x)(f-b \, g+i\,w \, p)=T(f_1-b \, g_1)-g_1\tag{1}$$ My professor says that $(1)$ can be solved by using Green's function $G(x,y)$, where $G(...
2
votes
3answers
2k views

Solve for variable in integral limit when using NIntegrate

I am trying to solve for a variable which appears in the limits of an integral, rather like in the following; ...
6
votes
4answers
654 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 ...
2
votes
1answer
150 views

NDSolve with different function lengths over time

I'm working on a cops & robbers game, and there is one single event that is very very important, the event of catching someone. I'm trying to do when any robber is catched, delete it from the ...
0
votes
1answer
79 views

How to ignore terms containing in the summation of multiplications

n=4;L=3; p0[n_Integer]:= Product[ Sum[Subscript[r, k][l, l], {l, L - 1}], {k, n}] // Expand; How to ignore terms containing three or more multiplications of [2, ...
0
votes
0answers
91 views

DSolve cannot solve for certain branches of the solution help pls

I get an error message while trying to compute this code.. help pls ...
0
votes
1answer
693 views

Symbolic matrix simplification and solving

I am trying to expand or solve an equation that contains matrices for a certain matrix, but it is not working: ...
14
votes
2answers
513 views

Behavior of Reduce with variables as domain

When using Reduce, I accidentally put a set of variables as the domain. To my surprise, it not only seems that Reduce expects ...
0
votes
1answer
239 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. ...
5
votes
2answers
267 views

How to “ReplaceAll” using a set of conditional expressions instead of a list of rules [closed]

Suppose that I have two linear functions f[x_] := f0 + f1 x g[x_] := g0 + g1 x and a (possibly rather complicated) set of conditional expressions, obtained ...
0
votes
2answers
52 views

Application on systems of equations [closed]

Lauren has 20 coins in her piggy bank, all dimes and quarters. The total amount of money is $3.05. How many of each coin does she have?
3
votes
1answer
535 views

Simulating a quick return mechanism

Last time, I got a satisfying answer for simulating a toggle mechanism, just as expected. NDSolve is great. I tried playing with it (as a matter of fact, @MichaelE2 ...
2
votes
2answers
310 views

Solving Inequalities with Gamma Function

I am wondering why Mathematica outputs that the following system "cannot be solved with the methods available to Reduce". $\frac{\Gamma(\frac{1}{2}+n)}{n-1}<\frac{\Gamma(\frac{1}{2}+k)}{k-1}$ ...
1
vote
1answer
488 views

Help to solve exponential equation over positive integers

I am trying to solve the equation $\frac{4}{9} = \big( \frac{1}{3} \big) ^n + \big( \frac{1}{3} \big) ^m $ with $n$ and $m$ both positive integers. I type into Mathematica the following In:= Solve[...
0
votes
0answers
207 views

Solve system of non commutative operators

I'd like to use mathematica to solve systems of linear equations, where the entries are non commutative matrices. I just tried the NC package but it doesn't help so far. For example I can solve: <...