To solve the given system of equations and determine which equation Berta found in step 1, let's proceed with a detailed, step-by-step solution:
Given the system of equations:
1. \( 4x + y = -5 \)
2. \( x - y = -5 \)
Step 1: Isolate \( y \) in the second equation
[tex]\[ x - y = -5 \][/tex]
[tex]\[ y = x + 5 \][/tex]
Step 2: Substitute \( y = x + 5 \) from the second equation into the first equation
[tex]\[ 4x + (x + 5) = -5 \][/tex]
This simplifies to:
[tex]\[ 4x + x + 5 = -5 \][/tex]
[tex]\[ 5x + 5 = -5 \][/tex]
Step 3: Solve for \( x \)
[tex]\[ 5x + 5 = -5 \][/tex]
Subtract 5 from both sides:
[tex]\[ 5x = -10 \][/tex]
Divide both sides by 5:
[tex]\[ x = -2 \][/tex]
Step 4: Substitute \( x = -2 \) back into the expression for \( y \)
[tex]\[ y = x + 5 \][/tex]
[tex]\[ y = -2 + 5 \][/tex]
[tex]\[ y = 3 \][/tex]
Berta determined that the solution is \((-2, 3)\). Therefore, the equation found in step 1 could have been:
[tex]\[ 5x = -10 \][/tex]
The correct choice from the given options is:
[tex]\[ 5x = -10 \][/tex]