Re: Rootfinding function (SOLVE) and guesses Message #14 Posted by Karl Schneider on 6 Aug 2010, 2:56 a.m., in response to message #13 by Don Shepherd
Quote:
Personally, I'd like the solver to do this for a quadratic equation: recognize that it's a quadratic, get the coefficients of x^2 and x and the constant term (a, b, and c), apply the quadratic formula, and return the two solutions (if there are two solutions) in x and y.
This requires that the equation be entered in full detail. And, what if the terms had not been gathered  should the calc still be able to recognize it as a quadratic? Any sophisticated solution will entail CAS.
I still say that the ideal solution is a polynomial solver, like that of the HP48G and its descendants: Choose "Solve Polynomial" from the SOLVE menu, enter [1 5 6], hit "Solve", and read 2 and 3 as the answers. A PC might be a better tool if the problem is more complicated than that.
A quadraticequation problem came up at work recently. After failing for a short while at simply reckoning an operating point, I derived a quadratic expression, programmed it as an equation on the HP32SII, and quickly solved it numerically, knowing what a realistic answer would look like. (The other solution, which I computed manually, was indeed unrealistic  well outside the operating limits of the equipment. The HP32SII found that one, too, with suitable guesses steering it in that direction.)
 KS
Edited: 8 Aug 2010, 2:21 a.m. after one or more responses were posted
