Got a bit of a confusing problem involving matrices.

We assume that is a Pythagorean triple, so that where are positive integers.

For P,

.

Show that:

, and are also Pythagorean triples.

Not sure where exactly to start here. Do I multiply them and then form some kind of equation, also a bit confused by the transposed bit at the start of the question?

Any points would be greatly appreciated

Thanks in advance