Answer
See below.
Work Step by Step
We multiply the matrices as follows:
$AB=\left[\begin{array}{c c} 2\cdot3.5+(-3)\cdot2& 2\cdot(-1.5)+(-3)\cdot(-1)\\ 4\cdot3.5+(-7)\cdot2& 4\cdot(-1.5)+(-7)\cdot(-1)\end{array} \right]=\left[\begin{array}{c c} 1& 0\\ 0& 1\end{array} \right]$
$BA=\left[\begin{array}{c c} 3.5\cdot2+(-1.5)\cdot4& 3.5\cdot(-3)+(-1.5)\cdot(-7)\\ 2\cdot2+(-1)\cdot4& 2\cdot(-3)+(-1)\cdot(-7)\end{array} \right]=\left[\begin{array}{c c} 1& 0\\ 0& 1\end{array} \right]$
Hence, we verified what we had to.