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Figure IV.10: Complex number calculations
The TI-89 can also solve for the real and complex solutions of an equation. This is done by using the
cSolve ( function which is found in the Algebra sub-menu of the MATH menu.
The format of cSolve ( is cSolve(expression, variable). For example, to find the zeros of
f x x3 4x2 14x 20, press 2nd MATH 9 [Algebra] alpha A [Complex] 1 [cSolve( ]. To complete
the computation, press X ^ 3 4 X ^ 2 + 14 X 20 0 , X) ENTER. The TI-89 will display real and
complex solutions of the equation, as shown in Figure IV.11.
Figure IV.11: cSolve function
Note that this calculation and the answer are too long for both the entry line and the history area. You can
scroll through the entire calculation or answer by using
or
to put the cursor on the appropriate line
and then using or to move the cursor to the part of the calculation or answer that you wish to see.
IV.2
Functions and Graphs
IV.2.1 Evaluating Functions: Suppose you receive a monthly salary of $1975 plus a commission of 10%
of sales. Let x your sales in dollars; then your wages W in dollars are given by the equation
W 1975 .10x. If your January sales were $2230 and your February sales were $1865, what was your
income during those months?
Here’s one method to use your TI-89 to perform this task. Press
Y= (above F1 key) or APPS 2
[Y= Editor] to display the function editing screen (Figure IV.12). You may enter as many as 99 different
functions for the TI-89 to use at one time. If there is already a function y1, press
or
as many times
as necessary to move the cursor to y1 and then press CLEAR to delete whatever was there. Then enter the
expression 1975 .10x by pressing these keys: 1975 + .10 X ENTER. Now press HOME.
Graphing Technology Guide
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IV-7