If the vertices of a parallelogram ABCD are A ( 1,2,3) . B ( -1,-2,-1) and C (2,3,2) then find the fourth vertex D.

Explanation

To find the fourth vertex \( D \) of the parallelogram \( ABCD \) given the vertices \( A(1, 2, 3) \), \( B(-1, -2, -1) \), and \( C(2, 3, 2) \), we can use the property that the diagonals of a parallelogram bisect each other.

### Step-by-step solution:

1. **Identify the coordinates of the known vertices**:
- \( A(1, 2, 3) \)
- \( B(-1, -2, -1) \)
- \( C(2, 3, 2) \)
...