to bring up the window where up to 99 equations may be entered.

.
To enter another equation, press
until an empty y= appears.
Press
to type the variable x.
Press
to type a leading negative sign.
Press
to type a subtraction symbol.
A equation can be selected or deselected by moving
the cursor to the equal sign of that equation and pressing
.
Deselected equations still exist but are not graphed.
Any character in an equation can be deleted. Highlight the character and press
.
Characters can be inserted in an equation. Highlight the entry after which the characters are to be
inserted. Press
.