Texas Instruments PLUS TI-89 - Manual (Page 75)

58 Chapter 3: Symbolic Manipulation
03SYMBOL.DOC TI-89/TI-92 Plus: Symbolic Manipulation (English) Susan Gullord Revised: 02/23/01 10:52 AM Printed: 02/23/01 2:12 PM Page 58 of 24
Steps
³
TI . 89
Keystrokes
›
TI . 92 Plus
Keystrokes Display
1. Display the Home screen and
clear the entry line. Solve the
equation
2x ì 3y = 4 for x .
„ 1 selects solve( from the Algebra
menu. You can also type solve(
directly from the keyboard or select it
from the Catalog.
"
M M
„ 1
2 X | 3 Y Á 4
b X d ¸ ¥ "
M M
„ 1
2 X | 3 Y Á 4
b X d ¸
2. Begin to solve the equation
ë x + 7y = ë 12 for y , but do not
press ¸ yet.
„ 1
· X « 7 Y Á
· 1 2 b Y d „ 1
· X « 7 Y Á
· 1 2 b Y d
3. Use the “with” operator to
substitute the expression for x
that was calculated from the
first equation. This gives the
value of
y .
The “with” operator is displayed as |
on the screen.
Use the auto-paste feature to
highlight the last answer in the history
area and paste it to the entry line.
Í
C ¸
¸ 2 Í
C ¸
¸
4. Highlight the equation for x in
the history area.
C C C C C C
5. Auto-paste the highlighted
expression to the entry line.
Then substitute the value of
y
that was calculated from the
second equation.
The solution is:
x = ë 8/11 and y = л 20/11
¸
Н
C ¸
¸ ¸
2 Í
C ¸
¸
This example is a demonstration of symbolic manipulation. A one-step function is available for
solving systems of equations. (See page 73.)
Preview of Symbolic Manipulation
Solve the system of equations 2x ì 3y = 4 and ë x + 7y = ë 12. Solve the first equation so
that x is expressed in terms of y. Substitute the expression for x into the second equation,
and solve for the value of y. Then substitute the y value back into the first equation to
solve for the value of x.