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 follow these steps:

### Step 1: Understand the properties of a parallelogram
In a parallelogram, the diagonals bisect each other. This means that the midpoint of diagonal \( AC \) is the same as the midpoint of diagonal \( BD \).

### Step 2: Find the midpoint of diagonal \( AC \)
The coordinates of points \( A \) and \( C \) are:
- \( A(1, 2, 3) \)
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