### The vertices A,B, and C of a triangle are given by the points (−1, 0, 2), (0, 1, 0), and (1,−1, 0), respectively. Find point D so that the figure ABCD forms a plane parallelogram.

**Answer:**If you have a parallelogram ABCD, then you know the vectors AB→ and DC→ need to be equal as they are parallel and have the same length. Since we know that AB→=(1,1,−2) you can easily calculate D since you (now) know C and CD→(=−A