HP 48g Graphing Calculator - Manual (Page 257)

Sometimes you may want to solve for a variable that’s stored in
another variable. To do this, you have to convert the algebraic so the
hidden variable is visible.
Sometimes you may want to speed evaluation by converting an
algebraic so all variables excepl certain ones are evaluated.
Showing Hidden Variables
1. Enter the expression onto the stack.
2. Do one of the following:
■ Enter the name (with ' delimiters) of the variable in the
expression that you do want to evaluate.
■ Enter a list containing the variable names in the expression that
you do not want e^■ aluated.
3. Press SYMBOLIC ) :Bhüh . The expression will be partially
evaluated according to your wishes in step 2.
To ewaluate an algebraic for temporary wariable ¥alues:
1. Enter the algebraic onto the stack.
2. Enter a list that contains each variable name followed by the value
to substitute. For example: { narnej erprp „ „ „ namXn expr„y
where expr can be a number or a symbolic expression.
3. Press
S3C
SYMBOLICI (IMXT ) 1 to perform the evaluation. If a
variable named in the list currently exists (in the VAR menu), its
contents are not changed by the | (“where”) function.
20
Rearranging Symbolic Expressions
Manipulating Whole Expressions
You can sometimes simplify algebraics by expanding subexpressions or
collecting like terms. For example, if a variable occurs more than once
in an algebraic, you may be able to simplify it so the variable occurs
only once—letting you use ISOL to solve for the variable.
Calculus and Symbolic Manipulation 20-17