Math Problem Statement

determine if b is a linear combination of a1, a2 and a3 a1 = [1;-2;0], a2 = [0;1;2], a3 = [5;-6;8], b= [2;-1;6]

Solution

To determine if b is a linear combination of a₁, a₂, and a₃, we need to check if there exist scalars x1,x2,x3x_1, x_2, x_3 such that:

x1a1+x2a2+x3a3=bx_1 \cdot a_1 + x_2 \cdot a_2 + x_3 \cdot a_3 = b

This can be written as the following matrix equation:

x1[120]+x2[012]+x3[568]=[216]x_1 \begin{bmatrix} 1 \\ -2 \\ 0 \end{bmatrix} + x_2 \begin{bmatrix} 0 \\ 1 \\ 2 \end{bmatrix} + x_3 \begin{bmatrix} 5 \\ -6 \\ 8 \end{bmatrix} = \begin{bmatrix} 2 \\ -1 \\ 6 \end{bmatrix}

This leads to the system of linear equations:

1. & \quad x_1 + 0x_2 + 5x_3 = 2 \\ 2. & \quad -2x_1 + x_2 - 6x_3 = -1 \\ 3. & \quad 0x_1 + 2x_2 + 8x_3 = 6 \end{aligned}$$ We will solve this system to determine whether a solution exists for $$x_1, x_2, x_3$$. Let me solve it.The solution to the system is given by: $$x_1 = 2 - 5x_3, \quad x_2 = 3 - 4x_3$$ This means that there are infinitely many solutions depending on the value of $$x_3$$. Therefore, **b** is a linear combination of $$a_1$$, $$a_2$$, and $$a_3$$, and the scalars $$x_1$$, $$x_2$$, and $$x_3$$ are not unique, but dependent on the value of $$x_3$$. Would you like more details, or do you have any questions? Here are five related questions you could explore: 1. How do you express the general form of linear combinations? 2. What is the geometric interpretation of a linear combination of vectors? 3. How can you determine if a set of vectors is linearly dependent? 4. What does it mean when a system of linear equations has infinitely many solutions? 5. Can you find a specific solution by assigning a value to $$x_3$$? **Tip:** When a system of equations has infinitely many solutions, it means the vectors involved are not linearly independent!

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Math Problem Analysis

Mathematical Concepts

Linear Algebra
Vector Spaces
Linear Combinations

Formulas

x1 * a1 + x2 * a2 + x3 * a3 = b
Matrix Equation: A * x = b

Theorems

Existence of solutions for systems of linear equations
Linear Dependence and Independence of Vectors

Suitable Grade Level

Undergraduate (Linear Algebra)