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Determine whether the set \(S\) is linearly independent or linearly dependent. \(S=\\{(6,2,1),(-1,3,2)\\}\)

Short Answer

Expert verified
The given set of vectors \(S=\{(6,2,1),(-1,3,2)\}\) is linearly independent.

Step by step solution

01

Write down the Matrix

Firstly, write down the matrix. The first row contains the coefficients from the first vector and the second row from the second vector. The resulting matrix \(A\) will be: \(A=\begin{bmatrix}6 & 2 & 1\\ -1 & 3 & 2\end{bmatrix}\)
02

Perform Gauss-Jordan Elimination

We will perform Gauss-Jordan elimination on this matrix to bring it to its Reduced Row Echelon Form (RREF). Start by swapping the rows to get the leading coefficient in the top row to be smaller (or negative, if possible). Next, add the first row to the second to avoid having a negative coefficient. Our goal is to have 1 as the leading coefficient in each row, and zero on all other elements of the column below and above the leading coefficients. This leads to an updated version of the matrix \(A\): \(A=\begin{bmatrix} -1 & 3 & 2\\6 & 2 & 1\end{bmatrix}\) and then \(A=\begin{bmatrix} -1 & 3 & 2\\0 & -16 & -11\end{bmatrix}\). Next, divide the second row by -16 to get leading coefficient 1, resulting in \(A=\begin{bmatrix} -1 & 3 & 2\\0 & 1 & \frac{11}{16}\end{bmatrix}\).
03

Convert the Initial -1 to 1 in the First Row

To complete the Gauss-Jordan elimination, multiply the first row by -1, so as to have 1 as the leading coefficient. The final matrix is then \(A=\begin{bmatrix} 1 & -3 & -2\\0 & 1 & \frac{11}{16}\end{bmatrix}\). After these steps, the matrix has now been row-reduced.
04

Determine the Linear Independence

In the final step, look at the row-reduced matrix. If any rows consist wholly of zeros, then the vectors were linearly dependent. However, in this matrix, no such row exists. Therefore, the vectors are linearly independent.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Gauss-Jordan Elimination
Gauss-Jordan Elimination is a method used to simplify matrices, making it easier to solve systems of linear equations. It involves performing specific row operations to transform the matrix into what is called Reduced Row Echelon Form (RREF). This method not only helps in solving equations but also in determining linear independence of vectors.

In our exercise, the matrix was initially constructed from vectors of set \(S\). The first step in Gauss-Jordan Elimination is often the swapping of rows, which can help position a smaller or negative leading coefficient at the top. This is a strategic move, making subsequent steps of elimination more straightforward.

After swapping, the next goal is to clear out all other elements in the column of the leading coefficient. Here, operations like adding or subtracting multiples of one row to another come into play, gradually simplifying the matrix until it's in a nearly solved state. Each step should ideally bring the matrix closer to having identity-like rows, which ultimately facilitates easy back substitution to solve for variables if needed.
Reduced Row Echelon Form (RREF)
A matrix in Reduced Row Echelon Form (RREF) is a crucial outcome of the Gauss-Jordan Elimination process. In this form, each leading coefficient is 1, and all elements above and below each leading 1 are zeros. Being able to spot RREF is important as it signals that the matrix has been fully simplified.

For our given matrix, after performing row operations, the final matrix becomes \(A=\begin{bmatrix} 1 & -3 & -2\0 & 1 & \frac{11}{16}\end{bmatrix}\). It closely resembles the identity matrix in terms of structure, which helps in confirming the status regarding linear independence.

The significance of having a matrix in RREF cannot be understated, as it simplifies analyzing linear dependencies. If a row of zeros is present after transforming a matrix to RREF, it implies that the vectors are dependent. Conversely, full non-zero rows, as seen in our scenario, indicate we have linearly independent vectors.
Matrix Row Operations
Matrix row operations are pivotal in altering matrices during processes like Gauss-Jordan Elimination. These operations include row swapping, scaling (multiplying a row by a non-zero constant), and pivoting (adding or subtracting the multiples of a row to/from another row). These operations transform the matrix to achieve a specific goal, such as solving systems of equations or determining linear independence.

Let's illustrate this with our exercise: the first row was swapped with the second, placing a preferable leading coefficient. Then row operations like adding one row to another helped eliminate undesired coefficients, turning the matrix closer to RREF.

By systematically applying these operations, we control the matrix's gradual progression toward a simplified form, ensuring accuracy in the process and enabling clearer analysis of the data involved. Matrix row operations form the fundamental toolkit for efficiently solving linear algebraic problems.

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Most popular questions from this chapter

Determine whether each statement is true or false. If a statement is true, give a reason or cite an appropriate statement from the text. If a statement is false, provide an example that shows the statement is not true in all cases or cite an appropriate statement from the text. (a) The column space of a matrix \(A\) is equal to the row space of \(A^{T}\) (b) The row space of a matrix \(A\) is equal to the column space of \(A^{T}\)

Determine whether the nonhomogeneous system \(A x=b\) is consistent. If it is, write the solution in the form \(\mathbf{x}=\mathbf{x}_{p}+\mathbf{x}_{\mathbf{k}},\) where \(\mathbf{x}_{\mathbf{p}}\) is a particular solution of \(\mathbf{A} \mathbf{x}=\mathbf{b}\) and \(x_{k}\) is a solution of \(A x=0\) $$ \begin{array}{l} 3 w-2 x+16 y-2 z=-7 \\ -w+5 x-14 y+18 z=29 \\ 3 w-x+14 y+2 z=1 \end{array} $$

(a) verify that each solution satisfies the differential equation, (b) test the set of solutions for linear independence, and (c) if the set is linearly independent, then write the general solution of the differential equation. $$ y^{\prime \prime \prime}+4 y^{\prime}=0 \quad\\{1,2 \cos 2 x, 2+\cos 2 x\\} $$

Determine whether the nonhomogeneous system \(A x=b\) is consistent. If it is, write the solution in the form \(\mathbf{x}=\mathbf{x}_{p}+\mathbf{x}_{\mathbf{k}},\) where \(\mathbf{x}_{\mathbf{p}}\) is a particular solution of \(\mathbf{A} \mathbf{x}=\mathbf{b}\) and \(x_{k}\) is a solution of \(A x=0\) $$ \begin{aligned} x_{1}+2 x_{2}+x_{3}+x_{4}+5 x_{3} &=0 \\ -5 x_{1}-10 x_{2}+3 x_{3}+3 x_{4}+55 x_{5} &=-8 \\ x_{1}+2 x_{2}+2 x_{3}-3 x_{4}-5 x_{5} &=14 \\ -x_{1}-2 x_{2}+x_{3}+x_{4}+15 x_{5} &=-2 \end{aligned} $$

Pendulum Consider a pendulum of length \(L\) that swings by the force of gravity only. For small values of \(\theta=\theta(t),\) the motion of the pendulum can be approximated by the differential equation $$ \frac{d^{2} \theta}{d t^{2}}+\frac{g}{L} \theta=0 $$ where \(g\) is the acceleration due to gravity. (a) Verify that $$ \\{\sin \sqrt{\frac{g}{L}} t, \cos \sqrt{\frac{g}{L}} t\\} $$ is a set of linearly independent solutions of the differential equation. (b) Find the general solution of the differential equation and show that it can be written in the form $$ \theta(t)=A \cos [\sqrt{\frac{g}{L}}(t+\phi)] $$

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