Question

Solve for x,y,z by elimination:

1)x-y+z=-1
x+y+3z=-3
2x-y+2z=0

2)x-y-2z=4
-x+2y+z=1
-x+y-3z=11

Answer 1

1. x=4, y=2, z=-3

2. x=0, y=2, z=-3

Answer 2

How did you get there? Can you show me the process please?

Answer 3

x-y+z=-1
x+y+3z=-3
---------------add
2x+4z=-4

x+y+3z=-3
2x-y+2z=0
--------------add
3x+5z=-3


(2x+4z=-4)*3
(3x+5z=-3)*2

6x+13z=-12
6x+10z=-6
-------------subtract
3z=-6
z=-3

3x+5z=-3
3x+5(-3)=-3
3x=-3+15
x= 12/3=4

x-y+z=-1
4-y-3=-1
y=4-3+1=2

you do the 2nd

Answer 4

So how do you know when to add or subtract or is it in that precise order (add, add, subtract)?