Question

Jika 2x-z=2, x+2y=4, dan y+z=1 maka nilai 3x+4y+z adalah...
a). 4
b). 5
c). 6
d). 7
e). 8

Answer 1

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

y + z = 1
z = - y + 1

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

2x + y = 3 |x1| 2x + y = 3
x + 2y = 4 |x2| 2x + 4y = 8
dieleminasikan menjadi -3y = -5 jadi y = 5/3

y + z = 1
5/3 + z = 1
z= 3/3 - 5/3 = -2/3

2x - z = 2
2x - (-2/3) = 2
2x = 6/3 - 2/3
2x = 4/3
x = 4/3 x 1/2 = 4/6 atau 2/3

jadi 3x+4y+z = 3(2/3) + 4(5/3) + (-2/3) = 2+20/3-2/3 = 6/3 - 2/3 + 20/3 = 24/3 = 8

jawabannya e