Solution 11932: Calculating the Inverse of a Matrix on theTI-83 Family, TI-84 Plus Family, or TI-Nspire™ Handheld in TI-84 Plus Mode.
How do I calculate the inverse of a matrix on a TI-83 family, TI-84 Plus family, or TI-Nspire handheld in TI-84 Plus mode?
The example below that will show how to calculate the inverse of a square matrix.
Example: Find the inverse of matrix A.
Solution: Enter the matrix:
1) Press [2nd] [MATRX] scroll to edit (On the TI-83, press the [MATRX])
2) Press 1
3) Input the dimensions of the matrix (2 [ENTER] 2 [ENTER])
4) Input the values for the elements of the matrix pressing [ENTER] after each entry
5) Press [2nd] [QUIT] to return to the home screen
To find the inverse of matrix A:
1) Press [2nd] [MATRX]  [x-1] [ENTER] (Press [MATRX]  [x-1] if using the TI-83)
Please Note: A singular matrix does not have an inverse. A singular matrix by definition is a matrix whose determinant equals zero.
Please see the TI-83 family and TI-84 Plus family guidebooks for additional information.
Please Note: TI-Nspire users may refer to the TI-84 Plus family guidebook.