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Berta worked to solve a system of equations.

[tex]\[
\begin{array}{c}
4x + y = -5 \\
x - y = -5
\end{array}
\][/tex]

Step 1: ???
Step 2: [tex]\( x = -2 \)[/tex]
Step 3: [tex]\( 4(-2) + y = -5 \)[/tex]
Step 4: [tex]\( -8 + y = -5 \)[/tex]
Step 5: [tex]\( y = 3 \)[/tex]

Berta determined that the solution is [tex]\((-2, 3)\)[/tex].

Which could have been the equation Berta found in step 1?

A. [tex]\(4x = 0\)[/tex]

B. [tex]\(5x = 10\)[/tex]

C. [tex]\(5x = -10\)[/tex]

D. [tex]\(5x = -25\)[/tex]


Sagot :

Sure, let's walk through the detailed step-by-step solution to identify the equation that Berta could have found in step 1.

Given system of equations:
[tex]\[ \begin{cases} 4x + y = -5 \\ x - y = -5 \end{cases} \][/tex]

### Step 1: Solve for y from the second equation

From the second equation [tex]\(x - y = -5\)[/tex], we can solve for [tex]\(y\)[/tex]:
[tex]\[y = x + 5\][/tex]

### Step 2: Substitute [tex]\(y\)[/tex] into the first equation

Now we substitute [tex]\(y = x + 5\)[/tex] into the first equation [tex]\(4x + y = -5\)[/tex]:
[tex]\[4x + (x + 5) = -5\][/tex]

### Step 3: Simplify the substituted equation

Combine like terms:
[tex]\[4x + x + 5 = -5\][/tex]
[tex]\[5x + 5 = -5\][/tex]

### Step 4: Isolate the variable [tex]\(x\)[/tex]

Subtract 5 from both sides:
[tex]\[5x = -10\][/tex]

This mean the potential equation Berta found in step 1 could have been:
[tex]\[5x = -10\][/tex]

Option: [tex]\[5x = -10\][/tex]

### Verification:
- From [tex]\(5x = -10\)[/tex], solving for [tex]\(x\)[/tex] we get [tex]\(x = -2\)[/tex].
- Substitute [tex]\(x = -2\)[/tex] back into the equation [tex]\(x - y = -5\)[/tex]:
[tex]\[-2 - y = -5\][/tex]
Solving for [tex]\(y\)[/tex], we get:
[tex]\[- y = -3 \implies y = 3\][/tex]

Berta's solution [tex]\((-2, 3)\)[/tex] checks out, confirming that the potential equation she found in step 1 is:
[tex]\[5x = -10\][/tex]

Thus, the correct option is:
[tex]\[\boxed{5x = -10}\][/tex]