Re: how-to with TI86 please?

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Re: how-to with TI86 please?

Reinier Zwitserloot wrote:
>
> if you are working with polynomials, use [2nd] [poly] gives you every
> single root there is, including double roots, and including complex
> roots. it's an eyeblink for 2nd and 3rd orders, and it takes a while
> on 10th orders, but, heck, if you do that by hand it would take you a
> year :-).
>
> If it isn't a polynomial, and you are sure it has just one root, use
> the solver. or, if you only need one root, use the solver.
>
> If it's none of the above, graph it, and use >|Math|root. now move
> your cursor towards the root you are interested in with the cursor
> keys, and hit enter. the thing newtonmethods it's way to the nearest
> root. the closer you are, the faster it'll fly.
>
> NB: There are some specific points between the attraction basin
> boundaries (usually found right in the middle of roots) that display
> chaotic behavior.
>
> NB2: the More, math,root, method doesn't find you any complex.

        Reinier,

        Your reply was a big help for some of the situations I have
encountered. As you seem to really know what you're talking about, I'll
pose a specific instance of something I still have trouble with:
        This equation: X^4-999.4*X^3-599.89*X^2-109.994*X-6=0  -- just like
this, with no parenthesis.
        Entered into the solver, it solves and shows me one root value - there
are three. By selecting GRAPH from the menu, I get an interesting graph
showing the line crossing the X-axis a few times. I can cursor over to
near an X intercept and select SOLVE from the menu, and it solves the
equation for the value of that point of the graph. So far so good.
        Now -- the problems: If I enter this equation in the normal (non
solver) screen, then press GRAPH key, I don't get a graph. But, if I use
the solver and select GRAPH, I don't get MATH (and thus I don't get
ROOT) from the menus onscreen.
        Is there a way to get to this from within the solver so I don't have to
exit the graph by selecting SOLVE from the menu? It seems a lot quicker
when I graph a linear equation in the normal screen and press GRAPH,
then following the method you suggest, select MATH and ROOT and cursor
to both sides of the X intercept. Can I do something like this with an
equation which requires SOLVER due to multiple roots?
        You mention polynomials... I'm not that far into my algebra class yet.
Would this equation I pose, with a few different roots, qualify as such
an expression?
        Thanks for your help - I do appreciate it. I've got an algebra teacher
who thinks the sun rises and sets on the TI83 and he can't (or won't)
help me figure this out.

        Russell Spreeman



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