Is there a faster way to find the roots of a polynomial using Horners method?

In summary: So i think the answer is: Deal with it as you can?No, the answer is that RRT is much faster at several cases than Horner, and that's what I answered above using computational complexity theory.No, the answer is that RRT is much faster at several cases than Horner, and that's what I answered above using computational complexity theory.
  • #1
theakdad
211
0
I have given polynomial: \(\displaystyle x^3-8x^2+19x-12\)

I know how to find the roots with Horners method,i am just wondering if there is an easier and quicker way to find them? Thank you!
 
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  • #2
wishmaster said:
I know how to find the roots with Horners method

You don't have to go that far. Try proving that this factors over integers completely by applying rational root theorem (integral root theorem for monic polynomials).
 
  • #3
mathbalarka said:
You don't have to go that far. Try proving that this factors over integers completely by applying rational root theorem (integral root theorem for monic polynomials).

I don't know how to do it...
 
  • #4
wishmaster said:
I have given polynomial: \(\displaystyle x^3-8x^2+19x-12\)

I know how to find the roots with Horners method,i am just wondering if there is an easier and quicker way to find them? Thank you!

The polynomial has degree 3, so that it exists at least one real root that can be found with the Newton-Raphson method...
 
  • #7
Find the divisors of \(\displaystyle 12\) then divide that by the divisors of the leading term \(\displaystyle 1\) so we have \(\displaystyle \pm 1 , \pm 3 , \pm 4 , \pm 6 \pm 12\) as possible roots.

\(\displaystyle P(3) = 3^3-8(9)+19\times 3-12 = 27-72+57-12=0 \)

Hence \(\displaystyle x=3\) is a solution . The next step divide the cubic by \(\displaystyle (x-3)\) to get a polynomial of degree $2$.
 
  • #8
Seems that's not the easier and faster method as Horners...or i can't see it! :D
 
  • #9
wishmaster said:
Seems that's not the easier and faster method as Horners...or i can't see it! :D

... not only neither easier nor faster... if the polynomial doesn't have rational roots [... the most probable case...] it fails!(Tmi)...

Kind regards

$\chi$ $\sigma$
 
  • #10
chisigma said:
... not only neither easier nor faster... if the polynomial doesn't have rational roots [... the most probable case...] it fails!(Tmi)...

Kind regards

$\chi$ $\sigma$

My question was about rational roots...how to find them fast. (Mmm)
 
  • #11
chisigma said:
neither easier nor faster

Horner's method has computational complexity $\mathcal{O}(n)$, whereas RRT exceeds that quite less often, as far as I can tell.
 
  • #12
mathbalarka said:
Horner's method has computational complexity $\mathcal{O}(n)$, whereas RRT exceeds that quite less often, as far as I can tell.

So i think the answer is: Deal with it as you can?
 
  • #13
Nope. I believe RRT is much faster at several cases than Horner, and that's what I answered above using computational complexity theory.
 

FAQ: Is there a faster way to find the roots of a polynomial using Horners method?

What are the roots of a polynomial?

The roots of a polynomial are the values of the variable that make the polynomial equal to zero.

How do you find the roots of a polynomial?

To find the roots of a polynomial, you can use various methods such as factoring, the quadratic formula, or synthetic division.

What is the relationship between the roots and factors of a polynomial?

The roots of a polynomial are the solutions to the polynomial equation, while the factors of a polynomial are the expressions that multiply together to make the polynomial. The roots and factors of a polynomial are related because the roots of a polynomial correspond to the factors of the polynomial equation.

Can a polynomial have more than one set of roots?

Yes, a polynomial can have multiple sets of roots depending on its degree. For example, a quadratic polynomial can have two distinct sets of roots, while a cubic polynomial can have three sets of roots.

Why are the roots of a polynomial important?

The roots of a polynomial are important because they provide valuable information about the behavior and characteristics of the polynomial. They can help determine the x-intercepts, the turning points, and the overall shape of the polynomial's graph.

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