For questions on or related to the technique of Gaussian elimination, used in solving systems of linear equations.

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Scale vector in scaled pivoting (numerical methods)

In the scaled pivoting version of Gaussian elimination, you exchange rows/columns not only based on the largest element to be found, but rather the largest relative to the entries in its row. You ...
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2answers
36 views

Is set of three linear equations with three unknown solvable?

I have the following set of linear equations with the unknowns $h, n, i$ which I would like to express as a function of my known quantities, $e, f, g$: $$ e = h - n\\ f = h - i\\ g = i -n $$ with ...
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1answer
20 views

Gaussian elimination problem

$$x_1 + 10x_2 − 3x_3 = 8$$ $$x_1 + 10x_2 + 2x_3 = 13$$ $$x_1 + 4x_2 + 2x_3 = 7$$ when making 2nd and 3rd 1st columns 0 using Gaussian elimination, the second row second column also becomes zero, so ...
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21 views

Gauss Jordan Elimination different answers

I have a question regarding Gauss Jordan Elimination. I have this matrix: \begin{bmatrix}2&1&5&0\\1&0&-3&1\\7&2&2&1\end{bmatrix} So at the start I will switch R1 ...
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1answer
10 views

Different results while calculating eigenvectors with Gaussian elemination

Regarding this matrix $\begin{matrix} 1 & 1 \\ 1 &-1 \\ \end{matrix}$. In the end I have to solve this equation system: $(\sqrt2-1)x_1-x_2=0$ $-x_1+(\sqrt2+1)x_2=0$ While the ...
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1answer
23 views

Why do the 1's in Gauss Jordan RREF need to be along main diagonal and not other diagonal?

I've practiced G-J elimination and understand most of the algorithm insofar as it represents the different manipulations one can apply to a system of equations. However, when we're talking about ...
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1answer
17 views

Finding the y-coordinate of the peak in a gaussian distribution?

First off all, my general understanding of gaussians is not very good, and I'm having issues getting my head around this because I cannot find an explanation of them I can understand. I'm working ...
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2answers
49 views

Propositions of elementary matrix

i'm trying to solve a question about elementary matrix. When given $A_{m,n}$ and $B_{n,p}$ which differ from the Zero matrix. Also, multiplying of $A$ and $B$ is the zero matrix, that is: $AB=0$; ...
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1answer
20 views

Working on pivots intuition

I am learning linear algebra using Gilbert Strangs "Intro to LA" 4th edition. On problem set for chapter 2.3 "Elimination Using Matrices" I encountered a question I can't wrap my head around(problem ...
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1answer
22 views

find Direction vector

i got this problem ( very trivial I guess) $39x -51y =15$ $-52x + 68 = -20$ I've done the Gauss reduction and got this, Matrix: \begin{pmatrix} 1 & \frac{-17}{13} & \frac{5}{13} \\ 0 ...
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1answer
50 views

Is there an easier way to find the inverse of a 3x3 matrix?

I know the normal process is to do row operations to transform the matrix to get the identity matrix and then apply the same row operations in the identity matrix to get the inverse. But this process ...
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Fast method or direct generation of random upper triangular matrix using integer-restricted gauss elimination

I'd like to generate non-singular random upper triangular matrices of the following form: $$ \left[\begin{matrix} 1 & r_1 \cos{\alpha_1} & r_2 \cos{\alpha_2} & r_3 \cos{\alpha_3} & ...
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2answers
35 views

Why does the Gaussian-Jordan elimination works when finding the inverse matrix?

In order to find the inverse matrix $A^{-1}$, one can apply Gaussian-Jordan elimination to the augmented matrix $$(A \mid I)$$ to obtain $$(I \mid C),$$ where $C$ is indeed $A^{-1}$. However, I fail ...
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22 views

Improving a Numerically Instable 6th Order Polynomial Fit Using Gaussian Elimination

I had a requirement to implement polynomial curve fitting in software, which I have done using multiple regression and Gaussian Elimination with Partial Pivoting. I have done this for 2nd, 5th and ...
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19 views

Constrained System of Equations

$Ax=b$ is a linear system of equations with dimension of $n$ in which $A$ is real, symmetric, and positive definite (RSPD). The matrix $A$ can be also written as \begin{equation} A_{n \times n} = G_{n ...
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35 views

Does gaussian elimination always work?

If so, why don't we use that to get from any square matrix to a triangular matrix - from which can be deduced eigenvalues, determinant (product of eigenvalues) and diagonal matrix (since the diagonal ...
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1answer
24 views

How to know what steps to perform when doing Gauss-Jordan reduction?

I am currently studying linear algebra at university. We are currently doing Inverses of matrices using Gauss-Jordan Reduction, but no one has really explained how you are supposed to decide what ERR ...
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2answers
43 views

Linear Equation Problem Solving

I'm confused on how you can approach this problem using Gauss-Jordan elimination. I’m buying three chemicals, call them A, B and C. One kg (kilogram) of A takes up 100 cc (cubic centimeters) and ...
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1answer
42 views

Thomas Algorithm for Tridiagonal System

A professor gave us an assignment to solve a Tridiagonal system using Thomas Algorithm. Here is the exercise: I am lost as to what to do with that $(0.2\pi)^2$ and do I just calculate the ...
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1answer
40 views

How to find the general solution to this matrix?

I am trying to find the general solution to this system of equations using an augmented matrix, and then using the gauss reduction technique, but i cant seem to get it into row echelon form no matter ...
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1answer
95 views

How to row reduce a matrix with complex entries?

I have been doing some practice questions for university, and one of them is regarding row reducing a complex matrix. From what I can work out, I think (i could very well be wrong) that the first ...
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5answers
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Determine inverse matrix of $\left(\begin{matrix} 0 & 3 \\ 0 & 6 \end{matrix} \right)$ using Gauss-Jordan method

I need to find the inverse of the following matrix with Gauss-Jordan method, but apparently, checking with a calculator, it does not exist: $$\left(\begin{matrix} 0 & 3 \\ 0 & 6 \end{matrix} ...
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3answers
39 views

Is there any sufficient or necessary conditions for a matrix to do Gaussian Elimination?

For now I know that we can do Gaussian elimination to $ m\times n $ matrices. But is there any restrictions?
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3answers
37 views

gaussian elimination to solve a question (using a paramter)

I want to solve : x2+x3=0 -x1 -x3=0 x1-x2 =0 I got the $x_1 = -t, x_2=-t, x_3=t$. But the book has $x_1 = t, x2=t, x3=-t$. ...
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2answers
74 views

Gauss elimination applied to a 4x2 system of equations

I have used Gauss elimination just for a while, and I am still not comfortable, and most of the times I do mistakes and I do not arrive the the right upper triangular matrix. I have problem which ...
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2answers
64 views

Why this system is not linear and how that influences the number of solutions?

I have an exercise in my last assignment for linear algebra, it's the following: This system is not linear, in some sense $$ 4sin(\alpha) + 3tan(\beta) + 2cos(\gamma) = 1 \\ -sin(\alpha) + ...
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0answers
23 views

Apply gauss method and write elementary iteration matrices

I have a problem where I have to apply the Gauss method to 2 simple linear system of equations and write the elementary iteration matrices that I use for solving the systems. One of the system is: ...
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1answer
28 views

Substitution Algebra: How to produce a “y equals” statement

$x + 3y = -4$ $y + x = 0$ What are $x$ and $y$? I know that in the first problem you replace the $y$ beside the $3$ but I cannot figure out how to turn $y + x = 0$ into a $y=$ statement
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Can we give efficiently the solution of a system of bilinear equations over a finite field?

Consider a finite field $F$ and suppose we have a system of equations $$h_1(\alpha,\beta)=0,h_2(\alpha,\beta)=0,...,h_t(\alpha,\beta)=0$$ where $\alpha=(\alpha_1,...,\alpha_s)$ and ...
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1answer
31 views

Gaussian elemination method question? Change rows if neccessary

We have the following system.I have to solve this using Gaussian elemination. We have here x1+x2+x4=2 2x1+x2-x3+x4=2 4x1-x2-2x3+2x4=0 3x1-x2-x3+2x4=-3 The augmented matrix is \begin{matrix} ...
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2answers
43 views

How do I verify that a set of vectors is a basis for the given plane

I have a set of 2 vectors: $\{ (1,2,0), (0,2,-1) \}$. I have to show that this set is a basis for the plane with equation: $2x_1 - x_2 -2x_3 = 0$. I know that the normal vector of the plane is ...
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2answers
41 views

Gauss-Jordan elimation unstable?

Well for finding the inverse of any matrix (by hand) I learned to use the "Guass-Jordan elimination". However today I was looking it up again on wolfram|alpha. And what struck me is the line: ...
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2answers
39 views

How do I row-reduce this matrix?

I've been trying for a while, but can't get the row reduced form. this is the matrix. $$\begin{bmatrix} 4 & 8 & 1 & 1 & 6\\ 3 & 6 & 1 & 2 & 5\\ 2 & 4 & 1 ...
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38 views

Proving Frobenius Theorem for Eigen Values

In my mulitivariable calculus class to justify second derivative test my professor used a theorem he called the frobenius theorem. But when I searched on wiki all I could find was Perron Frobenius ...
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Characteristic Polynomial Calculation

I have a problem in my homework in which I have to find the characteristic polynomial of the following matrix: I know the final solution is: However, my answer keeps getting wrong whenever I ...
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2answers
320 views

Why does Gaussian elimination not preserve similarity of a matrix?

I am trying to understand reduction of an unsymmetric real square matrix to Hessenberg form from Numerical Recipes Vol. 3. In it, the author states that one does not use Gaussian elimination for ...
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1answer
38 views

System of linear equation with one parameter

I'm trying to understand and solve a linear equation but i'm not sure how to go about it next, I was trying to reduce it with row operations but I can't seem to get all zero's under the first 'pivot' ...
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Gauss-Jordan elimination in the form of (A|I)

So Gauss-Jordan elimination can be performed through the form of $(A|I)$ where $I$ is the identity matrix. We carry out row elementary operations as usual until the matrix becomes the form $(I|B)$, ...
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2answers
36 views

Three equations, three unknowns, and one constraint

Suppose we have the following three equations: $$ r_y = \frac{r_y}{2} + \frac{r_a}{2} \\ r_a = \frac{r_y}{2} + r_m \\ r_m = \frac{r_a}{2} $$ We also have additional constraint for uniqueness: $$ r_y ...
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Premultiplication by an elimination matrix

Let $$A = \begin{bmatrix} 1 & 0 & 0 & 0 \\ 1 & 1 & 0 & 0 \\ 1 & 2 & 1 & 0 \\ 1 & 3 & 3 & 1 ...
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2answers
40 views

Gaussian Elimination Type Method Required

I'm struggling a bit with the following problem: $3 + 14x = 1 + 25y = 9 + 288z$ I have a series of these equations which I need to solve, with different first terms in each case and one of these ...
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32 views

LU factorisation

I am studying the LU factorisation. What I have learned is that with this technique we start with a matrix A and result into two matrices L and U where L is a Lower Triangular matrix and U is an Upper ...
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0answers
61 views

Where can Gaussian Elimination be used?

I have searched for this and came to know about it that it is traditionally used to solve linear equations, finding determinant, rank of matrix, inverse of matrix. There was a problem on codechef: ...
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Basis for span and transpose of span of matrix?

Does the rows of the RREF of the transpose of the span of a matrix yield a basis of a matrix ? Can a basis also be composed of the rows RREF of the span of a matrix ?
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1answer
120 views

Determine when the system has a) no solution, b) 1 solution and c) infinitely many solutions

This question is not for an assignment, it was on the midterm and I am interested in figuring out how to solve it before the final exam. cheers, Determine when the system has a) no solution, b) 1 ...
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1answer
46 views

How was step 1 done in Gaussian Elimination?

Suppose I have matrix $B:= \begin{bmatrix}4 & -2 & 2\\-2 & 5 & 3\\ 2 & 3 & 7 \end{bmatrix} $ Performing Gaussian Elimination we get: EDIT corrected mistake. I mistakenly ...
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2answers
88 views

Find the solution of binary xor operator equation

I am working in binary xor operator $\mathbb Z_2$. I have to resolve my problem such as $$\begin {cases} x_1+x_2+x_3=1\\ x_1+x_2=0\\ x_1+x_3=1\\ \end {cases}$$ Could you suggest to me any method to ...
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2answers
63 views

Solving a system of equations with less equations than variables

For my discrete math/linear algebra class, one of our homework problems reads as follows: ...
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33 views

How to find the basis of a matrix by using Gauss-Elliminaton?

I confuse that, This is my calculating process, Where i do the mistake in this process? I hope to understand this error.
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1answer
42 views

What is the computational cost of reduced row echelon and finding the null space?

I'm taking computational linear algebra, and haven't been able to find too much information about the computational cost (in terms of m=rows and n=cols) of these two routines: Reduced Row Echelon ...