Chapter 1.6, Problem 16E

(a)

To determine

To prove: Addition in $M_{m\times n}\left(ℝ\right)$ has the property that each element in $M_{m\times n}\left(ℝ\right)$ has an additive inverse in $M_{m\times n}\left(ℝ\right)$.

(b)

To determine

To prove: Addition is commutative in $M_{m\times n}\left(ℝ\right)$.