We have AB = = (61)(67)-(47)(87) = -2

Here determinant of matrix = |AB|≠ 0 hence (AB)^-1 exists.

Also |A| = 1 ≠ 0 and |B| = -2 ≠ 0.

∴ A^-1 and B^-1 will also exist and are given by-

And hence,

{Hence proved}