Question

What is the first step to solving this system of equations using the substitution method?
x+y=11
x=-y-9

add the equations together
Substitute -y-9 in for x in the top equation
substitute y=11 in for x in the bottom equation
substitute 11-x for the x in the bottom equation

Answer 1

To solve the system of equations using the substitution method, the first step is to **substitute \(-y - 9\) in for \(x\) in the top equation**.

Here's how that looks:

1. You have the equations:
- \(x + y = 11\)
- \(x = -y - 9\)

2. Substitute \(-y - 9\) for \(x\) in the first equation \(x + y = 11\):

\[
(-y - 9) + y = 11
\]

This substitution allows you to solve for \(y\) in a straightforward manner.

So, the correct choice is: **Substitute -y-9 in for x in the top equation.**