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

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0
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0answers
46 views

Solve gives solution with ComplexInfinity -> number

I am trying to solve a cumbersome equation using ...
0
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0answers
30 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
178 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 ...
4
votes
2answers
158 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
1answer
73 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 ...
0
votes
0answers
23 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
109 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 ...
0
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0answers
67 views
5
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1answer
115 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
1answer
120 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
votes
1answer
74 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
91 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. ...
6
votes
4answers
257 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 ...
1
vote
1answer
95 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 ...
2
votes
1answer
98 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} ...
0
votes
3answers
120 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.
11
votes
1answer
578 views

Proving inequalities with Mathematica

Question summary: I would like to learn some tips and tricks on how to prove inequalities with Mathematica. I'm studying various inequalities in triangle that have the form $R+ar + bs\geq 0$, where ...
5
votes
1answer
138 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 ...
2
votes
1answer
475 views

How could I define a function as the solution of equations in Mathematica?

I have posed a specific question yesterday but it may be too trivial to answer. I think the question could be asked in a more general way so it is easier to answer. Then I could solve the original ...
1
vote
4answers
162 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.
0
votes
6answers
299 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 ...
0
votes
1answer
68 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 ...
0
votes
0answers
46 views

NSolve solution does not verify original equation

I have been trying to find the solutions for an equation f(x)=0. This is a polynomial function of rank 3, so there should be three solutions. I have tried FindRoot and NSolve but the problem is the ...
0
votes
0answers
23 views

Jacobian matrix formation from polynomial expressions [duplicate]

I want to find the jacobian matrix for 3 polynomial expression with 3 variables.. the polynomial expressions have the degree of 8.how to form it.?
-1
votes
1answer
78 views

Solve set of non linear differential equations [closed]

I have set of differential equations. For example, I took two equations and tried to solve them as below. I am not getting any results. Please help me to figure it out the mistake. And I wonder if I ...
1
vote
1answer
76 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 ...
0
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0answers
41 views

Using Assumptions with Solve [duplicate]

Suppose i have a function defined as follows - f[x_] := E^-x - E^(-2 x); I want to find the max/min hence need to find when f'[x]==0. So i tried the following - ...
4
votes
2answers
675 views

Can mathematica solve this equation?

I have the following Mathematica code to solve an equation coming from isoparameteric finite element for quadratic tetrahedron element. I need to get the iteroplation fast and accurate. I only find ...
5
votes
2answers
329 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 ...
0
votes
0answers
132 views

Can Mathematica turn (y+x)=x^(1/y) into y=f(x)? [on hold]

I wanted to use Mathematica to turn a few implicit equations into explicit expressions. This worked fine for most of my equations, yielding mostly simple results and a few with a Lambert w function ...
10
votes
2answers
474 views

Finding all possible solutions to a math mind game

In the example below the letters shall be replaced by numbers. The numbers are from 1 to 9, and each letter has the same number ...
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
38 views

Error when solving equations constructed with Table [duplicate]

I have a couple of questions about the problem I am trying to solve ...
15
votes
4answers
1k views

How to get intersection values from a parametric graph?

I have this graphed: ParametricPlot[{2.4*Cos[t] + 1.6*Cos[3 t/2], 2.4*Sin[t] - 1.6 Sin[3 t/2]}, {t, 0, 4*Pi}] It is a star, and the lines cross each other ...
1
vote
1answer
300 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 ...
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
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0answers
52 views

Finding a certain invariant polynomial using matrix coordinates

Here's a math problem that I would like to solve. This is also my first time posting on the Mathematica stackexchange website so please excuse me if this looks messy. Let ...
0
votes
2answers
56 views

Help needed with Simple equations [closed]

take a simple formula like Ohm's law u=i*r... is it possible to solve for i without values??, something like Solve[u=i*r, i] and expect an output like i=u/r which gives me: Solve::naqs: i r is not ...
1
vote
3answers
149 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; ...
2
votes
1answer
94 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 ...
3
votes
2answers
144 views
1
vote
1answer
923 views

Solving functional equations in Mathematica

I am trying to solve functional equations in Mathematica, but got nowhere. Just a simple example: $$f(x+y)^2=f(x)^2+f(y)^2$$ for all $x,y \in R$, assuming f is a real-valued function. How should I ...
0
votes
1answer
116 views

how to find root near special root

I want to find the second root of this function ...
1
vote
0answers
194 views

Why is a bump function making NDSolve take forever to solve?

I am attempting to solve a system of relatively complicated elliptic PDEs via a relaxation technique. In particular, I am trying to solve $\textrm{div} LW = S$ where $S$ is some vector and $L$ is the ...
0
votes
0answers
44 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
40 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
1answer
109 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: ...
11
votes
2answers
474 views

How can I implement the method of Lagrange multipliers to find constrained extrema?

I want to form the function $h=f-\lambda_{1}g_{1}-\lambda_{2}g_{2}$ where $f$ is the function to optimize subject to the constraints $g_{1}=0$ and $g_{2}=0$ so that I can solve the first partial ...
7
votes
2answers
95 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 ...
-3
votes
2answers
66 views

Find the value by using FindRoot command [closed]

The equation x^4-3 x^3 = cos(3x)+3 has two real solutions on the interval from -10 to 10. Lets call these two solutions r and s. Use Mathematica's FindRoot command to find r and s. Now let M equal the ...