Question 9 (Multiple Choice Worth 2 points)
(Systems of Linear Equations MC)

Which ordered pair is a solution to the system of linear equations?

[tex]\[ \begin{cases}
x + 4y = 3 \\
y = -4x - 3
\end{cases} \][/tex]

A. [tex]\((1,1)\)[/tex]
B. [tex]\((1,-1)\)[/tex]
C. [tex]\((-1,1)\)[/tex]
D. [tex]\((-1,-1)\)[/tex]



Answer :

To determine which ordered pair is a solution to the system of linear equations, we need to check each pair to see if it satisfies both equations:

[tex]\[ \begin{array}{l} x + 4y = 3 \\ y = -4x - 3 \end{array} \][/tex]

Let's check each pair:

1. For the pair (1, 1):
[tex]\[ \begin{array}{l} x + 4y = 3 \\ 1 + 4(1) = 1 + 4 = 5 \quad \text{(not equal to 3, so this pair does not satisfy the first equation)} \end{array} \][/tex]
[tex]\[ \begin{array}{l} y = -4x - 3 \\ 1 = -4(1) - 3 = -4 - 3 = -7 \quad \text{(this pair does not satisfy the second equation either)} \end{array} \][/tex]
Thus, [tex]\((1, 1)\)[/tex] is not a solution.

2. For the pair (1, -1):
[tex]\[ \begin{array}{l} x + 4y = 3 \\ 1 + 4(-1) = 1 - 4 = -3 \quad \text{(not equal to 3, so this pair does not satisfy the first equation)} \end{array} \][/tex]
[tex]\[ \begin{array}{l} y = -4x - 3 \\ -1 = -4(1) - 3 = -4 - 3 = -7 \quad \text{(this pair does not satisfy the second equation either)} \end{array} \][/tex]
Thus, [tex]\((1, -1)\)[/tex] is not a solution.

3. For the pair (-1, 1):
[tex]\[ \begin{array}{l} x + 4y = 3 \\ -1 + 4(1) = -1 + 4 = 3 \quad \text{(this pair satisfies the first equation)} \end{array} \][/tex]
[tex]\[ \begin{array}{l} y = -4x - 3 \\ 1 = -4(-1) - 3 = 4 - 3 = 1 \quad \text{(this pair satisfies the second equation as well)} \end{array} \][/tex]
Thus, [tex]\((-1, 1)\)[/tex] is a solution.

4. For the pair (-1, -1):
[tex]\[ \begin{array}{l} x + 4y = 3 \\ -1 + 4(-1) = -1 - 4 = -5 \quad \text{(not equal to 3, so this pair does not satisfy the first equation)} \end{array} \][/tex]
[tex]\[ \begin{array}{l} y = -4x - 3 \\ -1 = -4(-1) - 3 = 4 - 3 = 1 \quad \text{(this pair does not satisfy the second equation either)} \end{array} \][/tex]
Thus, [tex]\((-1, -1)\)[/tex] is not a solution.

After checking each pair, we find that the only ordered pair that satisfies both equations is [tex]\((-1, 1)\)[/tex].

Thus, the correct answer is:

[tex]\[ \boxed{(-1, 1)} \][/tex]