Solve the following system of equations using both substitutio and elimination

Question

y=-x+4
y=-2x-4

Do I do what I do with the previous problems

Answer 1

I did the earlier ones with elimination
here is substitution
y = (-x+4)

so
(-x+4) = -2x - 4

x = -8
then go back and get y
y = -x + 4 = 8+4 = 12

Answer 2

for elimination subtract as is
y=-x+4
y=-2x-4
-------------
0 = 1 x + 8
so
x = -8
then get y = 8+4 = 12

Answer 3

I know where you get 1x but where did you get the +8 from

Answer 4

On the Elimination part

Answer 5

y = -x + 4
y = -(-8) + 4

Answer 6

So you first do 2x-x and get 1x. What do you do after that? Because I see it says 0=1 x + 8 but I still don't know how to get it

Answer 7

y=-x+4
y=-2x-4
------------- SUBTRACT these two equations
0 = -x -(-2x) + 4 - (-4)
0 = -x + 2x + 4 + 4
0 = x + 8
x = -8

Answer 8

I think I'm confused because this one is in Slope Intercept Form

Answer 9

Get it now. When you subtract you reverse the sign of the bottom one and add.

Answer 10

So when you plug in the x's as -8 would it be y=-x+4 and y=2(-8)-4