Find the inverses, and check … and …, for … and

Find the inverses, and check $A^{-1}A=I$ and $B{B}^{-1}=I$, for
$A=\left[\begin{array}{cc}1& 4\\ 0& 2\end{array}\right]$ and $B=\left[\begin{array}{cc}2& 2\\ 0& 1\end{array}\right]$.

Gilbert Strang, Calculus, 3rd edition (Wellesley-Cambridge Press; MIT OpenCourseWare RES.18-001) · §11.4 Matrices and Linear Equations, #33