algebra II, system of equations with three variables?
2x-3y+z=6
x-y+z=2
x-y-2z=8
answer is (4,0,-2). how do u get it? thank u so muchh
Favorite Answer
You have:
x-y+z = 2
So:
x = y-z+2
Now you also have:
2x -3y + z = 6
If you substitute x, it will become:
2(y-z+2) -3y +z = 6
2y – 2z + 4 – 3y + z = 6
(2- 3) y + (-2 + 1) z = 6 – 4
-y – z = 2
y + z = -2
y = -2 – z
Therefore, using the last equation:
x – y -2z = 8
(y – z + 2) – (-2 -z) – 2z = 8
(-2-z) – z + 2 + 2 +z -2z = 8
(-1 -1 + 1 -2)z -2 +2 + 2 = 8
-3z + 2 = 8
z = (8- 2) / -3
z = -2
Finally,
y = -2 – z
y = -2 – (-2)
y = -2 + 2
y = 0
and
x = y – z + 2
x = 0 +2 + 2
x = 4
So there you go (4, 0 , -2)
2x – 3y + z = 6 (First Equation)
x – y + z = 2 (Second Equation)
x – y – 2z = 8 (Third Equation)
Then;
Subtract equation 2 from equation 3
Thus,
(x – y – 2z = 8)
– (x – y + z = 2)
______________
-3z = 6
z = -2 (Answer)
Subtract equation 2 from equation 1
(2x – 3y + z = 6)
– (x – y + z = 2)
______________
x – 2y = 4
x = 4 + 2y (equation 4)
Consider equation 2…then substitute the values of z and x.
x – y + z = 2
4 + 2y – y + (-2) = 2
y = 0 (Answer)
Consider equation 4..then substitute the value of y
x = 4 + 2(0)
x = 4 (Answer)
Good luck!
2 -3 1 : 6
1 -1 1 : 2
1 -1 -2: 8
add row 3 times -1 plus row two
2 -3 1 : 6
1 -1 1 : 2
0 0 3 : -6
divide row three by 3
0 0 1 : -2 therefore z = -2
multipy row 2 by -2 then add to row one….
HOPE THAT HELPS
if no matrices—substitute
x = y – z + 2
x = y + 2z +8…
x-y+z=2
x=2+y-z
now fill in another equation using x
2+y-z-y-2z=8
2-3z=8
-3z=6
z=-2
now do the third using both
2(2+y–2)-3y+-2=6
4+2y+4-3y-2=6
6-y=6
-y=0
y=0
y=0,z=-2 and then we solve for x
x-0+-2=2
x-2=2
x=4
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