High School

Select the correct augmented matrices.

Liam wants to buy a car and pay for it in three installments. The total cost of the car is \[tex]$29,000.[/tex] Two times the first installment is \$1,000 more than the sum of the third installment and three times the second installment. Liam must pay 15% interest on the second and the third installments; the interest will amount to \$2,100. If [tex]x, y,[/tex] and [tex]z[/tex] represent the first, second, and third installments, respectively, identify the augmented matrices that model Liam's situation.

[tex]
\[
\begin{array}{ll}
\left[\begin{array}{ccc|r}
1 & 1 & 1 & 29000 \\
2 & -3 & -1 & 1000 \\
0.15 & 0.15 & 0.15 & 2100
\end{array}\right] &
\left[\begin{array}{rrr|r}
1 & 1 & 1 & 29000 \\
-3 & 2 & 0 & -15000 \\
0 & 1 & 1 & 14000
\end{array}\right] \\
\left[\begin{array}{ccc|r}
1 & 1 & 1 & 29000 \\
2 & -3 & -1 & 1000 \\
0 & 0.15 & 0.15 & 2100
\end{array}\right] &
\left[\begin{array}{rrr|r}
1 & 0 & 0 & 15000 \\
0 & 1 & 0 & 7500 \\
0 & 0 & 1 & 6500
\end{array}\right] \\
\left[\begin{array}{ccc|r}
1 & 0 & 0 & 15000 \\
0 & 1 & 0 & 8500 \\
0 & 0 & 1 & 5500
\end{array}\right]
\end{array}
\]
[/tex]

Answer :

To solve the problem, we need to set up equations based on the conditions given and identify which of the provided augmented matrices correspond to those equations.

### Step 1: Understand the Problem

Liam wants to pay for his car in three installments: [tex]\(x\)[/tex], [tex]\(y\)[/tex], and [tex]\(z\)[/tex], where:
- [tex]\(x\)[/tex] is the first installment.
- [tex]\(y\)[/tex] is the second installment.
- [tex]\(z\)[/tex] is the third installment.

We are given the following conditions:
1. The total cost of the car is [tex]\(\$29,000\)[/tex].
2. Two times the first installment ([tex]\(2x\)[/tex]) is [tex]\(\$1,000\)[/tex] more than the sum of the third installment ([tex]\(z\)[/tex]) and three times the second installment ([tex]\(3y\)[/tex]).
3. A [tex]\(15\%\)[/tex] interest is charged on the second and third installments, amounting to [tex]\(\$2,100\)[/tex].

### Step 2: Set Up the Equations

From the conditions, we can write the following equations:

1. Total Cost Equation:
[tex]\[
x + y + z = 29,000
\][/tex]

2. First Installment Equation:
[tex]\[
2x = 3y + z + 1,000
\][/tex]
Rearrange it to:
[tex]\[
2x - 3y - z = 1,000
\][/tex]

3. Interest Equation:
[tex]\[
0.15y + 0.15z = 2,100
\][/tex]
This can also be expressed as:
[tex]\[
0 \cdot x + 0.15y + 0.15z = 2,100
\][/tex]

### Step 3: Write the Augmented Matrix

Each equation corresponds to a row in the augmented matrix, resulting in:

[tex]\[
\begin{bmatrix}
1 & 1 & 1 & \vert & 29,000 \\
2 & -3 & -1 & \vert & 1,000 \\
0 & 0.15 & 0.15 & \vert & 2,100
\end{bmatrix}
\][/tex]

### Step 4: Match the Augmented Matrix to Given Options

Compare our derived augmented matrix with the given matrices. The correct matrices are:

- The matrix matches the setup we derived:
[tex]\[
\begin{bmatrix}
1 & 1 & 1 & \vert & 29,000 \\
2 & -3 & -1 & \vert & 1,000 \\
0 & 0.15 & 0.15 & \vert & 2,100
\end{bmatrix}
\][/tex]

This corresponds to the first and third matrices in the provided options.

So, the indices of the correct matrices are [0, 2].