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HP Forum Archive 14

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33s solving symmetrical quadratics
Message #1 Posted by bill platt on 28 July 2004, 9:45 a.m.

Hi,

Curious business. Try solving the simple expression n^2-6 on the 33s in the equation list.

It will return the positive root, but not the negative.

Try controlling the starting estimates by storing -10 to n, and -1 in the x-register. Still, a positive root. Try storing -1 in n, and -10 in the x-register. still, only a positive root!

On the 32sii, controlling the starting estimates "kicks" the solution over to the negative root.

Try a parabola that is shifted on the x-axis: v^2-v-6.

When you play with the initial estimates on this one, you DO get the negative root. Strange.

I wonder if this is related to the bizarrre "-0" issue which crops up in the cartesian to polar conversion issue.?

Regards,

Bill

      
Re: 33s solving symmetrical quadratics
Message #2 Posted by bill platt on 28 July 2004, 2:08 p.m.,
in response to message #1 by bill platt

But,

If you solve x^2 - 6 in either:

a program (RPN or ALG)

a program using an equation

You *can* push the solution across the zero to find the negative root.

Hmmmmm.....

Regards,

Bill

Edited: 28 July 2004, 2:09 p.m.


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