[tex]$
\begin{array}{l}
4x + 9y = 21 \\
3x - 8y = 1
\end{array}
$[/tex]

Choose the appropriate method to eliminate one variable:

A. Multiply the first equation by 3, and multiply the second equation by 4.

B. Multiply the first equation by -3, and multiply the second equation by -4.

C. Multiply the first equation by 8, and multiply the second equation by 9.

D. Multiply the first equation by -3, and multiply the second equation by 4.



Answer :

Certainly! Let's solve the given system of equations step-by-step as per the specified multiplications:

[tex]\[ \begin{array}{l} 4x + 9y = 21 \quad \text{(Equation 1)} \\ 3x - 8y = 1 \quad \text{(Equation 2)} \end{array} \][/tex]

Step 1: Multiply the first equation by 3 and the second equation by 4.

For the first equation:
[tex]\[ 3 \cdot (4x + 9y) = 3 \cdot 21 \\ 12x + 27y = 63 \][/tex]

For the second equation:
[tex]\[ 4 \cdot (3x - 8y) = 4 \cdot 1 \\ 12x - 32y = 4 \][/tex]

We now have:
[tex]\[ \begin{array}{l} 12x + 27y = 63 \\ 12x - 32y = 4 \end{array} \][/tex]

Step 2: Multiply the first equation by -3 and the second equation by -4.

For the first equation:
[tex]\[ -3 \cdot (4x + 9y) = -3 \cdot 21 \\ -12x - 27y = -63 \][/tex]

For the second equation:
[tex]\[ -4 \cdot (3x - 8y) = -4 \cdot 1 \\ -12x + 32y = -4 \][/tex]

We now have:
[tex]\[ \begin{array}{l} -12x - 27y = -63 \\ -12x + 32y = -4 \end{array} \][/tex]

Step 3: Multiply the first equation by 8 and the second equation by 9.

For the first equation:
[tex]\[ 8 \cdot (4x + 9y) = 8 \cdot 21 \\ 32x + 72y = 168 \][/tex]

For the second equation:
[tex]\[ 9 \cdot (3x - 8y) = 9 \cdot 1 \\ 27x - 72y = 9 \][/tex]

We now have:
[tex]\[ \begin{array}{l} 32x + 72y = 168 \\ 27x - 72y = 9 \end{array} \][/tex]

Step 4: Multiply the first equation by -3 again and the second equation by 4.

For the first equation:
[tex]\[ -3 \cdot (4x + 9y) = -3 \cdot 21 \\ -12x - 27y = -63 \][/tex]

For the second equation:
[tex]\[ 4 \cdot (3x - 8y) = 4 \cdot 1 \\ 12x - 32y = 4 \][/tex]

We now have:
[tex]\[ \begin{array}{l} -12x - 27y = -63 \\ 12x - 32y = 4 \end{array} \][/tex]

By carefully following the specified multiplications, we reach the results:
[tex]\[ (12, 27, 63, 12, -32, 4, -12, -27, -63, -12, 32, -4, 32, 72, 168, 27, -72, 9, -12, -27, -63, 12, -32, 4) \][/tex]