Texas Instruments TITANIUM TI-89 - Manual (Page 83)

Previews 83
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.
Steps and keystrokes Display
1. Display the Home screen and clear the
entry line. Solve the equation 2x N 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 .
Press " M M „ 1 2 X | 3 Y
Á 4 b X d ¸
2. Begin to solve the equation Lx + 7y = L12
for y, but do not press ¸ yet.
Press „ 1 ? X « 7 Y Á ? 12 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.
Press Í C ¸ ¸