HP 40G manual Root- Finder at work

If Solve could not find a solution, you will see one of the following two messages.

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.

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 62/9(ato start the root-finder, press any key except >21@. 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 >21@) and start over with a different initial guess.

Solve aplet 7-7