Program for finding roots and selecting one

[Eugenio]

(03-09-2016 02:43 AM)SlideRule Wrote:  Is this a PRIME specific question? otherwise, HP calculator programs for the solution of cubic equations go back to at least the HP-65 with program #7 in MATH PAC 1.

Kahan has two source locations on the topic:
a. To Solve a Real Cubic Equation
found at Cubic
b. To Solve A Real Cubic Equation
found at AD a206859

as well as Analytic Solution of Quartic & Cubic Polynomials by A J Helou, BCE, M.Sc., Ph.D.

BEST!
SlideRule

Thank you very much, and yes, its for the HP PRIME.

I was thinking to use the CAS.function('expression') to find the roots instead of programming a cubic root finder. My real problem is which command should I use in the programm so that when the CAS.function gives the 3 roots, the programm choses the only real root out of the 3 roots ( 2 complex and 1 real.) and then define that real root as the valua of "Z" so it follows its calculations.