Casio Scientific Calculator Fx-82es Plus "991es inverse matrix" Questions

...of the determinant of matrix by the inverse of matrix. Adjoint([A])= det( [A]) * [A]^-1. To get the inverse of a matrix, have its name displayed on command line then press the reciprocal key ...

991ES. Hello, The error may be due to the key you used to signifie inverse. It says in the manual that you should use the key x^-1 not the one used to input general powers. Here is screen capture from

...inverse of a 4X4 matrix on a casio 991es Sorry, this calculator can handle matrices with  dimensions ranging from 1X1 up to 3X3 . To deal with 4X4 matices you need a graphing calculator such as ...

...991ES offers simple matrix operations like basic arithmetic, plus the slightly more complex operations determinant and inversion. Furthermore, it is limited to matrices with a maximum size of three ...