Let

Then, define the plane . Determine which of the following points are on .

- ;
- ;
- ;
- ;
- .

First, we have

- The point is not on since
and

But then, .

- The point is not on since
and

But then, .

- The point is on since
and

Then, . Hence, for .

- The point is not on since
and

But then, .

- From part (d) we immediately see that is on .