HP 17bll+ User Manual page 180

The process of finding a solution iteratively is very complex. There are
four possible outcomes. Refer to "Solver Calculations" in appendix B for
additional descriptions of these outcomes.
Case 1: The calculator displays a result. It is very likely that this is a
solution to the equation. To check how good this result is, you can
repeat the calculation by pressing the menu key for the variable you
solved for. If the two sides of the equation have not been calculated to
be exactly equal, the calculator displays a message with the values
for the left and right sides of the equation. Read "Solver Calculations"
in appendix B for an explanation of the meaning of this display.
Case 2: The calculator displays a message with the calculated,
unequal values of the left and right sides of the equation. The Solver
has found a possible solution, but you must interpret its validity. To see
the questionable solution, press
Calculations" in appendix B for more information.
Case 3: The calculator displays                
           . The Solver cannot begin the search with the
current guesses. Press
supply new guesses, see "Entering Guesses," below.
Case 4: The calculator displays                 . Check
to see if your equation and stored values are correct. If the equation is
correct, you might be able to find a solution by entering very good
guesses.
Halting and Restarting the Iterative Search
When the Solver is iteratively searching for a solution (in other words,
when the Solver is displaying sets of estimates), you can halt the
calculation by pressing any key except
message            . To see the best estimate the Solver has
found so far, press
it left off by pressing the menu key for the variable you are solving for.
Or, you can restart the search using your own guesses (see "Entering
Guesses," below).
180 12: The Equation Solver
< or C
or . You can restart the search from where
C <
or . Refer to "Solver
< C
to view the starting guesses. To
. The calculator displays the
@