HP 39gs - Manual (Page 91)

Solve aplet 7-7
If Solve could not find a solution, you will see one of the
following two messages.
H I N T It is important to check the information relating to the
solve process. For example, the solution that the Solve
aplet finds is not a solution, but the closest that the
function gets to zero. Only by checking the information
will you know that this is the case.
The Root-Finder
at work
You can watch the process of the root-finder calculating
and searching for a root. Immediately after pressing
to start the root-finder, press any key except .
You will see two intermediate guesses and, to the left, the
sign of the expression evaluated at each guess. For
example:
+ 2 2.219330555745
– 1 21.31111111149
You can watch as the root-finder either finds a sign
reversal or converges on a local extrema or does not
converge at all. If there is no convergence in process, you
might want to cancel the operation (press
) and start
over with a different initial guess.
Plotting to find guesses
The main reason for plotting in the Solve aplet is to help
you find initial guesses and solutions for those equations
that have difficult-to-find or multiple solutions.
Consider the equation of motion for an accelerating
body:
Message Condition
Bad Guess(es) The initial guess lies outside the
domain of the equation.
Therefore, the solution was not a
real number or it caused an error.
Constant? The value of the equation is the
same at every point sampled.
2
2
0
AT
T V X + =
HP 39gs English.book Page 7 Wednesday, December 7, 2005 11:24 PM