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Easy question about exact results on screen
06-01-2016, 03:06 PM
Post: #1
Easy question about exact results on screen
Thank you in advance.
Trying to get zeros of this polinomy: x^3-x^2+0.5x-0.125, which settings allows me to get the exac form :1/2,(1+sqrt(3)*i)/4,(1-sqrt(3)*i)/4)??
The exact question would be, which settings bring the exact "answer" without decimals?


Thank you again!
Pedro ML
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06-01-2016, 03:21 PM
Post: #2
RE: Easy question about exact results on screen
To get exact results you need to use exact fractions for the numbers (for ex. 5/10) and not approximate decimal numbers such as 0.5
In CAS mode:
Code:
cSolve(x^3-x^2+(5/10)*x-(125/1000)=0,x)
will provide the exact result you're expecting.
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06-01-2016, 03:46 PM (This post was last modified: 06-01-2016 03:49 PM by salvomic.)
Post: #3
RE: Easy question about exact results on screen
if you use (in CAS: in Home I get [] -why?- ...)
cZeros(x^3-x^2+(½)*x-(⅛))
you get
[\( \frac{1}{2} \ \frac{1}{4}*(\sqrt{3}*i+1) \ \frac{1}{4}*(-\sqrt{3}*i+1) \)]

As you know, If you input .05, .0125 you'll get only [0.5]

I'm using CAS and check in the "complex" and "exact" items in Shift-CAS Settings...

Salvo

∫aL√0mic (IT9CLU), HP Prime 50g 41CX 71b 42s 12C 15C - DM42 WP34s :: Prime Soft. Lib
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06-01-2016, 04:23 PM
Post: #4
RE: Easy question about exact results on screen
Thank you so much Salvo, Didier.
Both answers are great, and incredible fast!!!

Best regards!
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06-01-2016, 04:33 PM (This post was last modified: 06-01-2016 04:41 PM by salvomic.)
Post: #5
RE: Easy question about exact results on screen
(06-01-2016 04:23 PM)PedroML Wrote:  Thank you so much Salvo, Didier.
Both answers are great, and incredible fast!!!

Best regards!

you're welcome :-)

also, Pedro, you can use (if you want) 0.5 and 1.125, and then, after getting the approx results, use QPI program (QPI by Han) to obtain the same symbolic results...

Hovewer, as Didier said, it's better use fractions instead of decimals for best results.

Salvo


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