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Given the system of equations:
[tex]\[
\begin{align*}
2x - 6y &= 20 \\
2x + 5y &= -11
\end{align*}
\][/tex]

What would you need to multiply the top equation by so that the x variables eliminate?

A. Multiply by -1
B. Multiply by 6
C. Multiply by 1
D. Multiply by -2


Sagot :

To solve the system of equations and eliminate the x variables, we need to ensure that the coefficients of x in both equations are equal in magnitude but opposite in sign.

Here are the given equations:

1) [tex]\(2x - 6y = 20\)[/tex]
2) [tex]\(2x + 5y = -11\)[/tex]

To eliminate the [tex]\(x\)[/tex] variables, we need to add or subtract the equations in such a way that the x terms cancel each other out.

First, let's consider multiplying the top equation by different possible values to see which one facilitates the elimination of [tex]\(x\)[/tex]:

1. Multiplying by -1:

[tex]\[ -1 \cdot (2x - 6y) = -1 \cdot 20 \implies -2x + 6y = -20 \][/tex]

Now, we can add this new equation to the second equation:

[tex]\[ (-2x + 6y) + (2x + 5y) = -20 + (-11) \implies 11y = -31 \][/tex]

This simplifies to:

[tex]\[ 11y = -31 \][/tex]

So, multiplying the top equation by -1 is the correct approach. It makes the coefficients of [tex]\(x\)[/tex] equal in magnitude and opposite in sign, allowing the [tex]\(x\)[/tex] terms to cancel out when the equations are added together.

Therefore, the correct answer is: Multiply by [tex]\(-1\)[/tex].