Is there an simple proof that shows:

1. Linear transformation of a polyhedron (i.e. the intersection of finitely many closed half-space) is a polyhedron.
2. Minkowski sum of two polyhedron is polyhedron.

I know a proof of (1.) based on Fourier-Motzkin elimination. and, I know (2.) is a simple consequence of (2.).

Every different approach is appreciated.