what matrix is formed when a matrix is pre-multiplied by its inverse matrix

Question

what matrix is formed when a matrix is pre-multiplied by its inverse matrix  I have no idea about this question it confuses me

Answer 1

 

The definition of an inverse matrix A^-1 is that   AA^-1 = A^-1A = I         So premultiplying A by A^-1 gives you I, the identity matrix.