Find out if the 3 positions are on the same line or not (3,2,0) (1, -1,2) (5,5, 2)

The three positions are not on the same line.

Step-by-step explanation:

We have three points: A:(3,2,0),  B:(1,-1,2) and C:(5,5,2).

Let's build a vector that goes from one point to another; that vector will be the director of a line (if we draw a vector that goes from A to B, that vector will be the direction of the line that pass by A and B because it does not change). In order to build that vector, let's subtract B from A:

The equation of a line is:

Where p is every singular point of the line, is a particular point of the line (any that we are sure that it is on the line), r is the director vector and t is the independent variable.

Now we have the director vector: (2,3,-2), and we can verify that A and B are on the line:

Because there is a value for t that satisfies both A and B: If we do and t=0, we are going to obtain the point p=A; and if we do t=-1, we are going to obtain p=B. Let's see that:

If C is also in the same line, C must accomplish the equation: , so:

Let's simplify the equation writing the parametric equation, which is just to write the equation for each dimension:

You can verify that there is not a value of t that satisfies all three equations, so, the point C is not on the same line as A and B; which means that A, B and C are not on the same line.