An operation is defined by p I q = 4pq? - q. Calculate the value of
21(-3).

These can be written in converse format:

If the shape is a parallelogram, then its opposite sides are parallel and congruent.

If the shape is a parallelorgram, then its opposite angles are congruent and adjacent angles are supplementary.

If the shape is a parallelorgram, then its diagonals are congruent.