Solve the system by substitution.

-x - y - z = -8
-4x + 4y + 5z + 7
2x + 2z + 4

Question

Solve the system by substitution.

-x - y - z = -8
-4x + 4y + 5z + 7
2x + 2z + 4

anonymous · Answer

I've done some of my work already. I'm just stuck now

anonymous · Answer

anonymous · Answer

hope this helps! :) @nicki96

anonymous · Answer

i understand how to do it, im just not sure if I did one of them right

aripotta · Answer

tell us what you got then

anonymous · Answer

ill give you the answers and you check if they are right :)

anonymous · Answer

do you want me to show you the work ive done so far?

aripotta · Answer

sure

anonymous · Answer

can you please check your equations again..they're not correct

anonymous · Answer

the second two dont have equal signs

anonymous · Answer

since i have to use substitution i solved for y in the first one and got x = -y - x + 8

anonymous · Answer

I meant to put = instead of the + sign, sorry

anonymous · Answer

okay so you should have gotten x=3, y=6, and z=-1
the rest Ari will help with :D

anonymous · Answer

I solved for x in the first one so I could substitute it in for x in the other equations

anonymous · Answer

okay thanks yummydum

aripotta · Answer

x = -y - x + 8 
i think you meant x = -y - z + 8

aripotta · Answer

so now we substitute that into the other two equations

anonymous · Answer

yeah that's what I meant

aripotta · Answer

-4( -y - z + 8) + 4y + 5z = 7

anonymous · Answer

okay for the second one I substituted it in and got 8y + 9z = 39

anonymous · Answer

Then for the third equation I got stuck on it

aripotta · Answer

2(-y - z + 8) + 2z = 4

anonymous · Answer

i got -2y -2z + 16 + 2z = 4

anonymous · Answer

But doesn't it cancel out z ?

aripotta · Answer

yes it does

anonymous · Answer

so you would have to solve for y?

aripotta · Answer

you have to subtract 16 on both sides first

anonymous · Answer

y = 6 is what I got

aripotta · Answer

yup

anonymous · Answer

then would you plug it into the second equation?

aripotta · Answer

so substitute that into 8y + 9z = 39 to solve for z

anonymous · Answer

ok

anonymous · Answer

i got z = -1

aripotta · Answer

yup. so now plug those numbers into any of the original equations to solve for x

anonymous · Answer

would you then plug both y and z into one of the original three equations?

aripotta · Answer

yes lol

anonymous · Answer

okay

anonymous · Answer

i got x = 3, so the answer would be (3,6,-1) ?

aripotta · Answer

yup

anonymous · Answer

yay! thank you for your help!

aripotta · Answer

no problem :)