Texas Instruments TI-83 Plus Manual Book page 33

Use options on this screen ... To do this:
MAIN displays the main menu.
BACK displays the SYSMATRIX screen so
that you can view or change the values.
STOsys stores the coefficients to a matrix
variable that you select.
Solution screen
STOx stores the solutions to a matrix
variable that you select.
MAIN displays the main menu.
BACK displays the matrix entry screen so
that you can view or change the values.
STOsys stores the coefficients to a matrix
variable that you select.
No Solution Found screen
RREF displays the reduced row-echelon
form of a matrix that has either no solution
or infinite solutions.
TI-83 Plus Polynomial Root Finder / Simultaneous Equation Solver Application Page 33