HP 39gs Master Manual page 328

Defining new variables
In addition to the pre-defined variables you can also define your own using the
new variables can have names that are more than one character long and can contain not only numbers but
objects such as algebraic expressions.
For example,
STORE(X
screen. If you now type
VARS
case sensitive, meaning that "
To release the memory taken up by a variable you no longer need, use the
example,
UNASSIGN(FRED)
can enter the screen and use the
VARS
view. Just highlight the variable and press
The functions
STORE
Entering and editing an expression
When entering an expression the main point to remember is that evaluations and appending of operations
are always done to the currently highlighted element. This is most easily seen with an example. A more
detailed explanation will then follow of how the CAS editing screen operates when entering and editing
expressions.
The task we will be performing in this first example will be to expand and then factorize the expression
( )( ) (
x − 4 x + 5 − x − 40
used to ensure that you can see exactly what is required. This will not be a general habit for this section.
i. Press , ,
Press and the expression will be enclosed automatically in brackets. If you had not highlighted the
entire expression first then only the 4 would be multiplied and no brackets would appear. Now add
another factor to the expression by pressing
, ,
Highlight the entire binomial expression by pressing
append another expression to this by pressing
, ,
At this point the screen should appear as shown right.
2
would define a new variable called "
-1,FRED)
FACTOR(FRED)
" and "
FRED Fred
will remove the variable and release the memory it takes up. Alternatively, you
and can both be found in the
UNASSIGN
)
over the set of complex numbers. In this first example images of the keys will be
then press
SHIFT
, .
, , , .
then the result would be
" would be regarded as two different variables.
(purge) command, which is one of the screen buttons in that
.
to highlight this expression.
then
SHIFT
328
command. These
STORE
" which will appear in the
FRED
.
. Variable names are
(X+1) (X-1)
command. For
UNASSIGN
menu.