Slopefields on the TI-85

Given a differential equation, say y' = 3x-y, here is how to make the TI-85 draw a slopefield for that differential equation.
 
  1. Put the calculator into Function mode: Press [2nd] [MODE] and select Func as shown:

  2. We must translate the differential equation: In place of the function (y in this case), write y (lower case), in place of y' write y1, and in place of the variable (x in this case), write x. So we get y1=3x-y.
  3. Now press [GRAPH][y(x)=] and enter our differential equation from the last step on the first line:
  4. Press [EXIT][RANGE] to select a suitable window or range.
  5. Press [EXIT][PRGM][NAMES] and select the SLPFE program.  Press [ENTER] to run it.
Last Modified December 3, 1998.
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