Answer
Calculate AB and BA.
Both products must be defined and equal $I_{n}$.
Work Step by Step
See definition on p.829:
Let A be an $\mathrm{n}\times \mathrm{n}$ square matrix.
If there is a square matrix $B$ such that
$AB=I_{n}$ and $BA=I_{n},$
then $B$ is the multiplicative inverse of $A$.
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Calculate AB and BA.
Both products must be defined and equal $I_{n}$.
