Jika titik A(6, 4, -2), B(4, 3, x), dan C(0, 1, 10) segaris, nilai x =..?

AB
= B - A
= (-2,-1,x+2)

BC
= C- B
=(-4,-2,10-x)

AB dan BC segaris, maka
AB = k.BC
(-2,-1,x+2) = k(-4,-2,10-x)

-4k = -2
k = 1/2

k(10-x) = x+2
1/2(10-x) = x+2
5 - 1/2x = x + 2
3/2x = 3
x = 3 * 2/3
x = 2