HP 39g+ - Manual (Page 155)

Using mathematical functions 10-19
Symbolic functions
The symbolic functions are used for symbolic manipulations
of expressions. The variables can be formal or numeric, but
the result is usually in symbolic form (not a number). You will
find the symbols for the symbolic functions = and | (where) in
the CHARS menu (
>6+,)7@
CHARS ) as well as the MATH menu.
= ( equals ) Sets an equality for an equation. This is not a logical operator
and does not store values. (See “Test functions” on page 10-
20.)
expression1=expression2
ISOLATE Isolates the first occurrence of variable in expression=0 and
returns a new expression, where variable=newexpression.
The result is a general solution that represents multiple
solutions by including the (formal) variables s1 to represent
any sign and n1 to represent any integer.
ISOLATE( expression , variable )
Examples
ISOLATE(2*X+8,X) returns -4
ISOLATE(A+B*X/C,X) returns -(A*C/B)
LINEAR? Tests whether expression is linear for the specified variable.
Returns
0 (false) or 1 (true).
LINEAR?( expression , variable )
Example
LINEAR?((X^2-1)/(X+1),X) returns 0
QUAD Solves quadratic expression=0 for variable and returns a new
expression, where variable=newexpression. The result is a
general solution that represents both positive and negative
solutions by including the formal variable S1 to represent any
sign: + or – .
QUAD( expression , variable )
Example
QUAD((X - 1)
2
-7,X) returns
(2+s1*5.29150262213)/2