Veda solves the following system of linear equations by elimination. What is the value of [tex]$x$[/tex] in the solution of the system of equations?

[tex]\[
\left\{
\begin{aligned}
6 + 4x - 2y & = 0 \\
-3 - 7y & = 10x
\end{aligned}
\right.
\][/tex]

A. -20
B. -1
C. 1
D. 20



Answer :

To find the value of [tex]\( x \)[/tex] in the solution of the given system of linear equations, follow these steps:

1. Write down the given equations:
[tex]\[ \left\{ \begin{aligned} 6 + 4x - 2y &= 0 \quad \text{(1)} \\ -3 - 7y &= 10x \quad \text{(2)} \end{aligned} \right. \][/tex]

2. Simplify the first equation:

First, we isolate one of the variables in Equation (1). Let's isolate [tex]\( y \)[/tex]:
[tex]\[ 6 + 4x - 2y = 0 \][/tex]
[tex]\[ 4x - 2y = -6 \][/tex]

3. Divide Equation (1) by 2 to further simplify:
[tex]\[ 2x - y = -3 \quad \text{(3)} \][/tex]

4. Rearrange Equation (2) for clarity:
[tex]\[ -3 - 7y = 10x \][/tex]
[tex]\[ 10x + 7y = -3 \quad \text{(4)} \][/tex]

5. We now have a system of two equations in simplified form:
[tex]\[ \left\{ \begin{aligned} 2x - y &= -3 \quad \text{(3)} \\ 10x + 7y &= -3 \quad \text{(4)} \end{aligned} \right. \][/tex]

6. Use the elimination method to solve for one of the variables. We will eliminate [tex]\( y \)[/tex].

Multiply Equation (3) by 7 to prepare for elimination:
[tex]\[ 7(2x - y) = 7(-3) \][/tex]
[tex]\[ 14x - 7y = -21 \quad \text{(5)} \][/tex]

7. Subtract Equation (5) from Equation (4) to eliminate [tex]\( y \)[/tex]:
[tex]\[ (10x + 7y) - (14x - 7y) = -3 - (-21) \][/tex]
[tex]\[ 10x + 7y - 14x + 7y = -3 + 21 \][/tex]
[tex]\[ -4x + 14y = 18 \][/tex]

8. Solve for [tex]\( x \)[/tex]:
Converting the equation for [tex]\( x \)[/tex], we find:
[tex]\[ -4x + 14y = 18 \][/tex]
Simplifying by isolating [tex]\( 4x \)[/tex]:
[tex]\[ -4x = 18 - 14y \][/tex]
Lastly, solving for [tex]\( x \)[/tex]:
[tex]\[ -4x = 18 - 14y \implies x = \frac{18 - 14y}{-4} = -1 \][/tex]

The value of [tex]\( x \)[/tex] in the solution of the system is:
[tex]\[ \boxed{-1} \][/tex]