Question

Annie wrote the following steps to solve a pair of equations:

Step 1: y = –x – 5
y = 2x + 2

Step 2: 2y = –2x –10
y = 2x + 2


Which of the following shows the correct next step to solve the equations by eliminating x?

Answer 1

Notice how we have -2x up top and 2x down below in step 2

also notice how -2x plus 2x = (-2+2)x = 0x = 0. So effectively, adding up the x terms in step 2 will make the x terms go away.

Answer 2

So you have do this with both sides

Adding the y terms on the left side gives 2y+y = 3y

adding up the constant terms on the right side gives -10+2 = -8

Answer 3

After adding up the two equations in step 2, we are left with

3y = -8