ab = 6
bc = 12
ca = 8
a + b + c = …?

Jawab :

ab = 6  …(1)
bc = 12 …(2)
ca = 8  … (3)

ab/bc = 6 / 12

a/c = 6/12 = 1/2 –> a = 1/2  c

masukkan ke (3) :

ca = 8 –> 1/2 c . c =  1/2 c² = 8

nilai c :

c² = 16 –> c = +/- 4

nilai a :

a = 1/2 c –> a = 1/2 (+/- 4) = +/- 2

nilai b :

ab = 6
b = 6/a –> 6/(+/- 2) = +/- 3

maka didapat nilai  a = +/- 2 ; b = +/- 3 dan c = +/- 4

sehingga

a + b + c = 2 + 3 + 4 = 9
atau

a + b + c = -2 – 3 – 4 = – 9