Math Problem Statement

In R^4, is v = [2, -1, 3, 0] a linear combination of v1 = [1, 3, 2, 0], v2 = [5, 1, 2, 4], and v3 = [-1, 0, 2, 1]?

Solution

To determine if the vector v=[2130]\mathbf{v} = \begin{bmatrix} 2 \\ -1 \\ 3 \\ 0 \end{bmatrix} is a linear combination of the vectors v1=[1320]\mathbf{v}_1 = \begin{bmatrix} 1 \\ 3 \\ 2 \\ 0 \end{bmatrix}, v2=[5124]\mathbf{v}_2 = \begin{bmatrix} 5 \\ 1 \\ 2 \\ 4 \end{bmatrix}, and v3=[1021]\mathbf{v}_3 = \begin{bmatrix} -1 \\ 0 \\ 2 \\ 1 \end{bmatrix}, we need to solve the following system of linear equations:

c1v1+c2v2+c3v3=vc_1 \mathbf{v}_1 + c_2 \mathbf{v}_2 + c_3 \mathbf{v}_3 = \mathbf{v}

This translates to the matrix equation:

c1[1320]+c2[5124]+c3[1021]=[2130]c_1 \begin{bmatrix} 1 \\ 3 \\ 2 \\ 0 \end{bmatrix} + c_2 \begin{bmatrix} 5 \\ 1 \\ 2 \\ 4 \end{bmatrix} + c_3 \begin{bmatrix} -1 \\ 0 \\ 2 \\ 1 \end{bmatrix} = \begin{bmatrix} 2 \\ -1 \\ 3 \\ 0 \end{bmatrix}

Or, more explicitly:

[151310222041][c1c2c3]=[2130]\begin{bmatrix} 1 & 5 & -1 \\ 3 & 1 & 0 \\ 2 & 2 & 2 \\ 0 & 4 & 1 \end{bmatrix} \begin{bmatrix} c_1 \\ c_2 \\ c_3 \end{bmatrix} = \begin{bmatrix} 2 \\ -1 \\ 3 \\ 0 \end{bmatrix}

Now, we solve this system using either Gaussian elimination or matrix inversion.

I'll proceed with solving it for you.The solution to the system of equations is approximately:

c10.0067,c20.2937,c30.5232c_1 \approx -0.0067, \quad c_2 \approx 0.2937, \quad c_3 \approx 0.5232

However, the system has a non-zero residual of about 7.54, which indicates that the vector v=[2130]\mathbf{v} = \begin{bmatrix} 2 \\ -1 \\ 3 \\ 0 \end{bmatrix} is not an exact linear combination of v1\mathbf{v}_1, v2\mathbf{v}_2, and v3\mathbf{v}_3.

Would you like a deeper explanation of these results or further details?

Here are some related questions you might explore:

  1. What does it mean for a vector to be a linear combination of others?
  2. How does Gaussian elimination work for solving linear systems?
  3. What is the significance of the residual in a least squares solution?
  4. Can we always solve any system of linear equations?
  5. How does matrix rank affect the solvability of systems?

Tip: Non-zero residuals in least squares indicate the system is overdetermined or inconsistent.

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Math Problem Analysis

Mathematical Concepts

Linear Algebra
Linear Combination
Matrix Equation
Gaussian Elimination

Formulas

c1 * v1 + c2 * v2 + c3 * v3 = v
Matrix equation: A * c = v where A is the matrix formed by v1, v2, v3

Theorems

Linear Combination
Gaussian Elimination

Suitable Grade Level

Undergraduate / High School (Grades 11-12)