Is there a simple proof that shows:

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

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

Every different approach is appreciated.

Is there a simple proof that shows:

1. Linear transformation of a $\mathcal{H}$-polyhedron (i.e. the intersection of finitely many closed half-spaces) is a $\mathcal{H}$-polyhedron.
2. Minkowski sum of two $\mathcal{H}$-polyhedrons is a $\mathcal{H}$-polyhedron.

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

Every different approach is appreciated.

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.

Is there a simple proof that shows:

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

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

Every different approach is appreciated.