The Museum of HP Calculators

HP Forum Archive 21

 ROOT bug? HP 48S/48GMessage #1 Posted by Eddie W. Shore on 11 July 2012, 9:01 a.m. 'X^3+5*X^2-2*X+7' 'X' 0 ROOT Returns .189254744132. (not a root, f(x) returns about 7) But using the poly solver... [1,5,-2,7] gives the correct answers: (approximately) (.29141, -1.08117), (.29141, 1.08117), -5.58283

 Re: ROOT bug? HP 48S/48GMessage #2 Posted by Luiz C. Vieira (Brazil) on 11 July 2012, 9:57 a.m.,in response to message #1 by Eddie W. Shore Hi. I did not check it, but wouldn't it be a pole?

 Re: ROOT bug? HP 48S/48GMessage #3 Posted by Les Koller on 11 July 2012, 12:59 p.m.,in response to message #1 by Eddie W. Shore If you read on the ROOT function of the advanced users manual, it shows you that you enter 1: function 2)variable to solve for 3) guess. The number returned is either the ROOT or the Local EXTREMA. There is a local minimum at x = .189....what your answer was. 0 (your guess) is closer to this value than the actual roots, that's why ROOT gave this answer for this specific guess.

 Re: ROOT bug? HP 48S/48GMessage #4 Posted by Eddie W. Shore on 11 July 2012, 2:57 p.m.,in response to message #3 by Les Koller Quote: If you read on the ROOT function of the advanced users manual, it shows you that you enter 1: function 2)variable to solve for 3) guess. The number returned is either the ROOT or the Local EXTREMA. There is a local minimum at x = .189....what your answer was. 0 (your guess) is closer to this value than the actual roots, that's why ROOT gave this answer for this specific guess. Good to know: thank you Les. I'll have to modify my program accordingly.

 Re: ROOT bug? HP 48S/48GMessage #5 Posted by Les Koller on 11 July 2012, 3:01 p.m.,in response to message #4 by Eddie W. Shore :)

 Re: ROOT bug? HP 48S/48GMessage #6 Posted by Gilles Carpentier on 13 July 2012, 4:03 a.m.,in response to message #1 by Eddie W. Shore Same result with the 50G, using ROOT Note that on the 50G, in approx mode : 'X^3+5*X^2-2*X+7' SOLVEVX gave the 3 roots (in complex mode, 1 in real mode) { 'X=(.291415279138,-1.08116667823)' 'X=(.291415279138,1.08116667823)' 'X=(-5.58283055828,0.)' } but is unable to find the exact roots I don't remember if SOLVEVX exists in 48 series [link:http://www.wolframalpha.com/input/?i=%27X^3%2B5*X^2-2*X%2B7%3D0%27]Wolfram math[/link] Edited: 13 July 2012, 4:22 a.m.

 Re: ROOT bug? HP 48S/48GMessage #7 Posted by Les Koller on 13 July 2012, 5:07 p.m.,in response to message #6 by Gilles Carpentier Yes, same result on 50G here too, which is what prompted me to go to the Advanced UM. :)

 Re: ROOT bug? HP 48S/48GMessage #8 Posted by Les Koller on 13 July 2012, 5:17 p.m.,in response to message #6 by Gilles Carpentier Looks like, from the manual, the 48GX does not have solvevx.

 Re: ROOT bug? HP 48S/48GMessage #9 Posted by Eddie W. Shore on 13 July 2012, 7:05 p.m.,in response to message #6 by Gilles Carpentier Quote: Same result with the 50G, using ROOT Note that on the 50G, in approx mode : 'X^3+5*X^2-2*X+7' SOLVEVX gave the 3 roots (in complex mode, 1 in real mode) { 'X=(.291415279138,-1.08116667823)' 'X=(.291415279138,1.08116667823)' 'X=(-5.58283055828,0.)' } but is unable to find the exact roots I don't remember if SOLVEVX exists in 48 series [link:http://www.wolframalpha.com/input/?i=%27X^3%2B5*X^2-2*X%2B7%3D0%27]Wolfram math[/link] I think SOLVEVX started with the HP 49G, not in the 48 series.

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