## Pivoting Program for TI-85/86

This program allows you to pivot on any entry in a matrix, and also to perform a simplification step (divide any row by a number). Thus, it is a useful way of checking your work, or dealing with large matrices and big numbers. (Note that the program will often come up with a multiple of the row you may get by pivoting manually, so you may wish to perform additional simplifiction steps to compare it with your manual work.)

Consult your graphing calculator manual for keystroke instructions to enter the following program. (Also see the supplementary materials for *Finite Mathematics Applied to the Real World, * or *Finite Mathematics and Calculus Applied to the Real World * for additional discussion on using a graphing calculator to pivot.

PROGRAM:PIVOT
:AB
:Lbl Z
:
:Pause A
:Disp "1 TO PIVOT"
:Disp "2 TO DIVIDE"
:Disp "3 TO REVERT"
:Disp "4 TO STOP"
:Input V
:
:If V==4
:Then
:Stop
:End
:
:If V==3
:Then
:BA
:End
:
:If V==1
:Then
:Input ("ROW ",R)
:Input ("COLUMN ",C)
:A(R,C)P
:dim AT
:T(1)N
:For(I,1,N,1)
:If IR
:Then
:If A(I,C)0
:Then
:A(I,C)X
:multR(P,A,I)A
:mRAdd(-X,A,R,I)A
:If P<0
:Then
:multR(-1,A,I)A
:End
:
:End
:End
:End
:End
:
:If V==2
:Then
:Input ("DIVIDE ROW ",R)
:Input ("BY ",X)
:multR(1/X,A,R)A
:End
:
:Goto Z

**To Run the Program**

Before running the program listed above, make sure that your matrix is entered under the name A. (To do this, use the [2nd] MATRIX key and choose EDIT A.) When you run the program and the matrix is displayed, you can use the arrow keys to view hidden parts of the matrix, and then press ENTER to continue the program. In either program, press 1 ENTER to pivot, 2 ENTER to do a simplification step (or to turn the pivots into 1's when you are done. Note that you can also multiply a row by a number: just divide by the reciprocal of the number) 3 ENTER to revert back to the matrtix you started with, and 4 ENTER to terminate.

Main Page
Last Updated:* April, 2000*
Copyright © 1997 StefanWaner and Steven R. Costenoble