HP 39g Graphing Calculator - Manual (Page 89)

Use an initial guess
Number
format
You can usually obtain a faster and more accurate solution if
you supply an estimated value for the unknown variable
before pressing ¡fflHi. Solve starts looking for a solution at
the initial guess.
Before plotting, make sure the unknown variable is
highlighted in the numeric view. Plot the equation to help you
select an initial guess when you don’t know the range in which
to look for the solution. See “Plotting to find guesses” on
page 7-8 for further information.
H I N T An initial guess is especially important in the case of a curve
that could have more than one solution. In this case, only the
solution closest to the initial guess is returned.
You can change the number format for the Solve aplet in the
Numeric Setup view. The options are the same as in Home
MODES: Standard, Fixed, Scientific, and Engineering. For
the latter three, you also specify how many digits of accuracy
you want. See “Mode settings” on page 1-9 for more
information.
You might find it handy to set a different number format for
the Solve aplet if, for example, you define equations to solve
for the value of money. A number format of Fixed 2 would
be appropriate in this case.
Solve aplet 7-5