HP 39gs Master Manual page 171

FNROOT(<expression>,<variable>,<guess>)
This function is like a mini version of the Solve aplet. If you feed it an
algebraic expression and an initial guess it will start from your guess and
find the value which makes the expression zero. Don't bother. It's a lot
easier to use the Solve aplet. This is a tool for programmers so that they
can access the Solve abilities within programs.
You need to tell it what variable is the active one in the expression, in
addition to providing it with an initial guess. If there is only one answer
then any guess will do, but if more than one solution is possible then
more care needs to be taken with your guess to ensure that it is in the
neighborhood of your desired solution.
Eg. (a) Solve x −
2
3x 5
Use:
d
(b) Solve
− =
5
3
Use:
As with Solve, if your expression involves more than one variable then whatever values are currently in
memory are used for the other variables.
See also: ,
QUAD POLYROOT
FRAC(<num>)
This function gives the decimal part of any number, discarding the integer part.
Eg. = 0.45
FRAC(3.45)
FRAC(1234.03456)
See also: ,
INT FLOOR
− = 0
2
FNROOT(X -3X-5,X,2)
3 d
+1
4
FNROOT(D/3-5-3D/4-1,D,0)
= 0.03456
, , ,
CEILING ROUND
,
TRUNCATE FRAC
171