eq. 1 2x+ y = -4
eq. 2 -2y+4z = 0
eq. 3 3x -2z = -11
The first equation has no z-term.
So eliminate z from the other two terms.
Multiply eq. 3 by 2 and add term by term:
-2y+4z = 0
6x -4z = -22
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6x-2y = -22
Divide that through by 2
eq. 4 3x- y = -11
Now we have a system of two equations and two
unknowns:
eq. 1 2x+y = -4
eq. 4 3x-y = -11
We add them term by term and y will be eliminated:
eq. 1 2x+y = -4
eq. 4 3x-y = -11
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5x = -15
x = -3
Substitute x = -3 in eq. 4,
eq. 4 3x-y = -11
3(-3)-y = -11
-9-y = -11
-y = -2
y = 2
Substitute x = -3 in eq. 3
eq. 3 3x-2z = -11
3(-3)-2z = -11
-9-2z = -11
-2z = -2
z = 1
Solution (x,y,z) = (-3,2,1)
Edwin
