Which system is equivalent to
[tex]\[
\left\{
\begin{array}{l}
5x^2 + 6y^2 = 50 \\
7x^2 + 2y^2 = 10
\end{array}
\right.
\][/tex]?

A.
[tex]\[
\left\{
\begin{array}{r}
5x^2 + 6y^2 = 50 \\
-21x^2 - 6y^2 = 10
\end{array}
\right.
\][/tex]

B.
[tex]\[
\left\{
\begin{aligned}
5x^2 + 6y^2 &= 50 \\
-21x^2 - 6y^2 &= 30
\end{aligned}
\right.
\][/tex]

C.
[tex]\[
\left\{
\begin{array}{l}
35x^2 + 42y^2 = 250 \\
-35x^2 - 10y^2 = -50
\end{array}
\right.
\][/tex]

D.
[tex]\[
\left\{
\begin{array}{l}
35x^2 + 42y^2 = 350 \\
-35x^2 - 10y^2 = -50
\end{array}
\right.
\][/tex]



Answer :

To determine which system is equivalent to the given system of equations:

[tex]\[ \begin{cases} 5x^2 + 6y^2 = 50 \\ 7x^2 + 2y^2 = 10 \end{cases} \][/tex]

We need to verify each of the four provided systems step by step.

Step 1: Verify the first system:
[tex]\[ \begin{cases} 5x^2 + 6y^2 = 50 \\ -21x^2 - 6y^2 = 10 \end{cases} \][/tex]

This system can be rewritten for comparison:
- The first equation remains: \( 5x^2 + 6y^2 = 50 \).
- Simplify the second equation to identify if it aligns with the given original equations:
[tex]\[ -21x^2 - 6y^2 = 10 \Rightarrow \text{not equivalent to } 7x^2 + 2y^2 = 10 \][/tex]

This system is NOT equivalent.

Step 2: Verify the second system:
[tex]\[ \begin{cases} 5x^2 + 6y^2 = 50 \\ -21x^2 - 6y^2 = 30 \end{cases} \][/tex]

This system can be rewritten for comparison:
- The first equation remains: \( 5x^2 + 6y^2 = 50 \).
- Simplify the second equation to identify if it aligns with the given original equation:
[tex]\[ -21x^2 - 6y^2 = 30 \Rightarrow \text{not equivalent to } 7x^2 + 2y^2 = 10 \][/tex]

This system is NOT equivalent.

Step 3: Verify the third system:
[tex]\[ \begin{cases} 35x^2 + 42y^2 = 250 \\ -35x^2 - 10y^2 = -50 \end{cases} \][/tex]

This system can be rewritten for comparison:
- The first equation from the given system, when multiplied by 7, becomes:
[tex]\[ 7 \cdot (5x^2 + 6y^2) = 7 \cdot 50 \Rightarrow 35x^2 + 42y^2 = 350 \text{ (not 250)} \][/tex]

This system is NOT equivalent.

Step 4: Verify the fourth system:
[tex]\[ \begin{cases} 35x^2 + 42y^2 = 350 \\ -35x^2 - 10y^2 = -50 \end{cases} \][/tex]

This system can be rewritten for comparison:
- The first equation from the given system, when multiplied by 7, becomes:
[tex]\[ 7 \cdot (5x^2 + 6y^2) = 7 \cdot 50 \Rightarrow 35x^2 + 42y^2 = 350 \][/tex]
This is equivalent.

- The second equation from the given system, when multiplied by 5, becomes:
[tex]\[ 5 \cdot (7x^2 + 2y^2) = 5 \cdot 10 \Rightarrow 35x^2 + 10y^2 = 50 \][/tex]
When rearranged to an equivalent form with a negative sign, it is:
[tex]\[ -35x^2 - 10y^2 = -50 \][/tex]
Which matches the second equation in this system.

Thus, the fourth system is equivalent.

Conclusion:
The system equivalent to the given one is:
[tex]\[ \left\{\begin{array}{l} 35x^2 + 42y^2 = 350 \\ -35x^2 - 10y^2 = -50 \end{array}\right. \][/tex]