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Three equations, three unknowns

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1. x+3y=2
-2x+3y+z=-1
y+z=-1

z=-1-y
x=2-3y

-2(2-3y)+3y+(-1-y)=-1
8y-5=-1
y=2

z=-1-2
z=-3

x=2-3(2)
x=-4

Can anyone see where I have gone wrong as my answers do not match the equations if plugged back in.
2. (Original post by Gorrilaz)
x+3y=2
-2(2-3y)+3y+(1-y)=-1
8y-5=-1
You messed up here.

When you multiply out the brackets, you should have gotten:
-4 + 6y + 3y + 1 - y = -1

which simplifies to

8y - 3 = -1
You messed up here.

When you multiply out the brackets, you should have gotten:
-4 + 6y + 3y + 1 - y = -1

which simplifies to

8y - 3 = -1
No sorry it was actually-4+6y+3y-1-y=-1

As z=-1 -y I just write that part wrong.
4. (Original post by Gorrilaz)
8y-5=-1
y=2
Your mistake is above. 8*2 does not equal 4.
Your mistake is above. 8*2 does not equal 4.
Haha wow how did it take me so long to spot.
6. (Original post by Gorrilaz)
Haha wow how did it take me so long to spot.
You're welcome.

Sometimes the simplest things are hardest to spot.
7. Unless I'm badly mistaken, you can find all 3 variables from the first 3 equations given. Or is this one of those questions where you have to do it a given way?
8. (Original post by AtomSmasher)
Unless I'm badly mistaken, you can find all 3 variables from the first 3 equations given. Or is this one of those questions where you have to do it a given way?
The equations after the first 3 are working out, they're just rearranged to make x and z in terms of y.
9. I've been trying this another way but I just can't get to y = 2. Even when I put y = 2 to get x and z I get values that don't work out. Where am I going wrong?! Are y'all sure these equations are self consistent?????
10. (Original post by fire sale)
I've been trying this another way but I just can't get to y = 2. Even when I put y = 2 to get x and z I get values that don't work out. Where am I going wrong?! Are y'all sure these equations are self consistent?????
y=0.5 i did it wrong lol

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