grandes-ecoles 2021 Q1

grandes-ecoles · France · centrale-maths1__mp Matrices Matrix Norm, Convergence, and Inequality
Show that, for every $M$ in $\mathcal{M}_{n}(\mathbb{R})$ and for all $P$ and $Q$ in $\mathcal{O}_{n}(\mathbb{R})$, we have $\|PMQ\|_{F} = \|M\|_{F}$.
Show that, for every $M$ in $\mathcal{M}_{n}(\mathbb{R})$ and for all $P$ and $Q$ in $\mathcal{O}_{n}(\mathbb{R})$, we have $\|PMQ\|_{F} = \|M\|_{F}$.