Soal Matematika bantu kerja no. 1, 3 dan 4

1. x + y=1............... x=1-y pers 3
2x + 4y =1
subsitusi x ke pers 2
2x + 4y =1
2(1-y) + 4y=1
2-2y+4y=1
2+2y=1
2y=1-2
2y=-1
y=-1/2
subsitusi y ke pers 3
x=1-y
x=1 - (-1/2)
x= 3/2


2. x - 2y + 3z=10
2x + y - 2z =11
2x +3y - z =-1

eliminasi pers 1 dan 2.
x - 2y + 3z = 10 |x2| 2x - 4y + 6z =20
2x + y - 2z = 11 |x1| 2x + y -2z =11
________________-
-5y + 8z =9... pers 4



eliminasi pers 2 dan 3.
2x + y.- 2z =11
2x + 3y - z=-1
______________-
-2y - z=12.... pers 5.


elimonasi pers 4 dan 5.
-5y + 8z =9 |x1| -5y + 8z =9
-2y - z=12. |x8| -16y -8z=96
______________-
-21y. =105
y=-5
subsitusi y ke pers 4.
-5y +8z =9
-5(-5) +8z=9
25 +8z=9
8z=9-25
8z=-16
z=-2


subsitusi y dan z ke peers 1.
x-2y+3z=10
x-2(-5)+3(-2)=10
x + 10 - 6=10
x + 4=10
x = 10-4
x = 6

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

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

subsitusi y ke pers 2
-2z +y +z=-2
-2z +1+z=-2
-z+1=-2
-z=-2-1
-z=-3
z=3


subsitusi y dan z ke pers 4.
x = 1+2y-z
x = 1+2(1)-3
x = 1+2-3
x = 0