(1 1) · (x1) = (3) (2 2) (x2) (6)

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Understand the Problem

The question involves a matrix multiplication equation, where a 2x2 matrix is multiplied by a column vector, resulting in another column vector. The goal is to find the values of x1 and x2 that satisfy the equation.

Answer

The solutions are $ (x_1, x_2) = (3, 0) $ or any other pairs satisfying $ x_1 + x_2 = 3 $.
Answer for screen readers

The solutions for the system of equations are $(x_1, x_2) = (3, 0)$, but there are infinitely many solutions such as $(x_1, x_2) = (2, 1)$, $(1, 2)$, etc.

Steps to Solve

  1. Set up the equation from the matrix multiplication

The equation can be set up based on the matrix multiplication of the 2x2 matrix and the column vector:

$$ \begin{pmatrix} 1 & 1 \ 2 & 2 \end{pmatrix} \begin{pmatrix} x_1 \ x_2 \end{pmatrix}

\begin{pmatrix} 3 \ 6 \end{pmatrix} $$

  1. Write the equations based on the multiplication

The multiplication leads to two equations:

From the first row: $$ 1 \cdot x_1 + 1 \cdot x_2 = 3 $$ From the second row: $$ 2 \cdot x_1 + 2 \cdot x_2 = 6 $$

  1. Simplify the second equation

Divide the entire second equation by 2 to simplify it:

$$ x_1 + x_2 = 3 $$

  1. Solve the system of equations

Now we have:

  • From the first equation: $x_1 + x_2 = 3$
  • From the simplified second equation: $x_1 + x_2 = 3$

Both equations are the same; thus, we can express one variable in terms of the other.

Let’s solve for $x_1$:

$$ x_1 = 3 - x_2 $$

  1. Choose a value for $x_2$

Choose any value for $x_2$. For example, if we let $x_2 = 0$, then: $$ x_1 = 3 - 0 = 3 $$

Thus one solution is $(x_1, x_2) = (3, 0)$. You could choose any value for $x_2$ to find other solutions.

The solutions for the system of equations are $(x_1, x_2) = (3, 0)$, but there are infinitely many solutions such as $(x_1, x_2) = (2, 1)$, $(1, 2)$, etc.

More Information

This represents a case of dependent equations, where there are infinitely many solutions along the line described by the equation $x_1 + x_2 = 3$.

Tips

  • Not recognizing that the second equation simplifies to the first, leading to the conclusion that there are infinitely many solutions.
  • Failing to choose a specific $x_2$ value when expressing $x_1$ in terms of $x_2$.

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