b. 1/x + 2/y = 1 1/x + 4/z = 0 1/y + 2/z = 1

jawab
a = 1/x
b = 1/y
c =1/z

1/x+ 2/y = 1 → a + 2b = 1
1/x + 4/z =0 → a + 4c = 0
1/y + 2/z = 1 →  b + 2c = 1

a + 2b = 1
a + 4c = 0  |(-)
b - 4c = 1

b - 4c = 1
b + 2c = 1 | (-)
-6c = 0
c = 0

b - 4c = 1
b - 4(0)= 1
b = 1

a+ 2b = 1
a +2(1) = 1
a = - 1

x =1/a = -1
y = 1/b= 1
z = 1/c = ∞