You can easily solve equations using the TI-89 graphing calculator. The
key decision for the user is whether to work in the real or the complex number
system. For example, let’s solve the quadratic equation, 2x^{2}
- 5x +12 = 0.

To solve the equation in the
real number system, press **F2** to select
the algebra menu, press **1** to select **1:solve(**
, enter the equation, then press **,**
(comma) **X** **)** **ENTER**.
The TI-89 responds with the answer **false**, indicating that this equation has
no real roots.

To obtain the complex roots, follow the above procedure
with the following exception. Instead of selecting 1:solve(
, select **A:Complex ****„**,
then select **1:cSolve**. The complex roots are

In particular, note that the option 1:solve yields solutions only in the real number system; whereas, cSolve yields solutions in the complex number system.

You may also solve an equation with a constraint. This is handy, for
example, in solving trigonometric equations. For example, let’s solve
sin(2*q** *) = 1 for 0
£ *q* < 2p. The appropriate syntax is:

solve(equation,variable) | constraint.

Here, the entry line is

solve(sin(2x)=1,x) | 0 £ x and x < 2p

Consult the test menu for details on how to enter inequalities and the “and”.