Math Problem Statement

Let A =   2 −4 −3 5 1 −3   and ⃗b =   10 −10 10   . A linear transformation T : R 2 → R 3 is defined by T(x) = Ax. Find an ⃗x in R 2 whose image under T is ⃗b. [ x1 x2 ] = [ ]

Solution

To solve the problem, we are tasked with finding a vector x=[x1x2]R2\mathbf{x} = \begin{bmatrix} x_1 \\ x_2 \end{bmatrix} \in \mathbb{R}^2 such that the linear transformation T(x)=Ax=bT(\mathbf{x}) = A \mathbf{x} = \mathbf{b}, where:

A=[243513],b=[101010].A = \begin{bmatrix} 2 & -4 \\ -3 & 5 \\ 1 & -3 \end{bmatrix}, \quad \mathbf{b} = \begin{bmatrix} 10 \\ -10 \\ 10 \end{bmatrix}.

This involves solving the matrix equation:

Ax=b.A \mathbf{x} = \mathbf{b}.

Step 1: Write the equation in component form

[243513][x1x2]=[101010].\begin{bmatrix} 2 & -4 \\ -3 & 5 \\ 1 & -3 \end{bmatrix} \begin{bmatrix} x_1 \\ x_2 \end{bmatrix} = \begin{bmatrix} 10 \\ -10 \\ 10 \end{bmatrix}.

In expanded form, this results in the following system of equations:

  1. 2x14x2=102x_1 - 4x_2 = 10,
  2. 3x1+5x2=10-3x_1 + 5x_2 = -10,
  3. x13x2=10x_1 - 3x_2 = 10.

Step 2: Solve the system

The system is overdetermined, so we solve the first two equations and verify consistency with the third.

Solve the first two equations:

  1. From 2x14x2=102x_1 - 4x_2 = 10, divide through by 2: x12x2=5.x_1 - 2x_2 = 5.

  2. Rewrite as: x1=5+2x2.x_1 = 5 + 2x_2.

  3. Substitute x1=5+2x2x_1 = 5 + 2x_2 into the second equation 3x1+5x2=10-3x_1 + 5x_2 = -10: 3(5+2x2)+5x2=10.-3(5 + 2x_2) + 5x_2 = -10.

  4. Simplify: 156x2+5x2=10.-15 - 6x_2 + 5x_2 = -10.

    15x2=10.-15 - x_2 = -10.

    x2=5.x_2 = -5.

  5. Substitute x2=5x_2 = -5 into x1=5+2x2x_1 = 5 + 2x_2: x1=5+2(5)=510=5.x_1 = 5 + 2(-5) = 5 - 10 = -5.

Thus, x=[55]\mathbf{x} = \begin{bmatrix} -5 \\ -5 \end{bmatrix}.

Step 3: Verify the solution

Substitute x=[55]\mathbf{x} = \begin{bmatrix} -5 \\ -5 \end{bmatrix} into the third equation x13x2=10x_1 - 3x_2 = 10: 53(5)=5+15=10.-5 - 3(-5) = -5 + 15 = 10.

The solution satisfies all three equations.

Final Answer:

x=[55].\mathbf{x} = \begin{bmatrix} -5 \\ -5 \end{bmatrix}.


Would you like a detailed step-by-step explanation of any part?
Here are 5 related questions to expand on this topic:

  1. How do you determine if an overdetermined system has a solution?
  2. What is the geometric interpretation of a linear transformation T:R2R3T: \mathbb{R}^2 \to \mathbb{R}^3?
  3. How do you find the rank of a matrix?
  4. How can we confirm if a given matrix is invertible?
  5. What are the implications of consistency in a linear system?

Tip: Always check the rank of the coefficient matrix to ensure the system is consistent before solving.

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Math Problem Analysis

Mathematical Concepts

Linear Algebra
Matrix Multiplication
Systems of Linear Equations

Formulas

Matrix equation: A⃗x = ⃗b
System of equations derived from matrix multiplication
Substitution method for solving systems of equations

Theorems

Consistency of Linear Systems
Properties of Matrix Transformations

Suitable Grade Level

Undergraduate (Linear Algebra Level)