Texas TI-86 Manuel D’Utilisation

15EQSOLV.DOC   TI-86, Chap 15, US English   Bob Fedorisko   Revised: 02/13/01 2:34 PM   Printed: 02/13/01 3:04 PM   Page 205 of 12

15EQSOLV.DOC   TI-86, Chap 15, US English   Bob Fedorisko   Revised: 02/13/01 2:34 PM   Printed: 02/13/01 3:04 PM   Page 205 of 12

The TI

-86 solves equations through an iterative process. To control that process, you can

enter lower bounds and upper bounds that are close to the solution, and enter a guess
within those bounds in the prompt for the unknown variable.

Controlling the process with specific bounds and a guess helps the TI

-86 in two ways.

♦ 

It finds a solution more quickly.

♦ 

It is more likely to find the solution you want when an equation has multiple solutions.

To set more precise bounds at the 

 prompt, the syntax is:

At the prompt for the unknown variable, you may enter a guess or a list of two guesses. If
you do not enter a guess, the TI

-86 uses (lowerBound+upperBound)à2 as a guess.

On the solver graph (page 207), you can guess a solution by moving the free-moving cursor
or trace cursor to a point on the graph between lowerBound and upperBound. To solve for
the unknown variable using the new guess, select 

 from the solver graph menu. The

solution is displayed on the interactive-solver editor.

To edit the equation stored to 

 when the interactive-solver editor is displayed, press $

until the cursor is on the equation. The equation-entry editor is displayed. The TI

-86

automatically stores the edited equation to 

 as you edit.

If you store an equation to 

 by recalling the contents of an equation variable, such as 

,

and then edit the equation stored to 

, the original equation (in 

, for example) is not

changed. Likewise, subsequently editing the contents of the equation variable (

, for

example) does not change 

.

<

must be true.

You can enter a list variable
at the 

 prompt if a

valid two-element list is
stored to it.

If you exit the equation
solver, any equation stored to
eqn is displayed when you
return to the equation solver.