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# Is there a "method" for finding Factors of polynomials INSTEAD OF GUESSING?

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1. How can I find a factor of a polynomial instead of guessing which takes time?
Is there a method?

Could you show me a method for finding the factor of:
f(x) = x^3 - 3x^2 + 20
2. (Original post by Adorable98)
How can I find a factor of a polynomial instead of guessing which takes time?
Is there a method?

Could you show me a method for finding the factor of:
f(x) = x^3 - 3x^2 + 20
Rational root theorem tells us that the only possible integer roots are which narrows it down considerably. It doesn't take long to see that works.

So nope, not really. You'll have to guess. Unless you want to learn the cubic formula off by heart, but... yeah.
3. (Original post by Adorable98)
How can I find a factor of a polynomial instead of guessing which takes time?
Is there a method?

Could you show me a method for finding the factor of:
f(x) = x^3 - 3x^2 + 20
Ruffini's rule, which is the method described by the user before me.
4. (Original post by Zacken)
Rational root theorem tells us that the only possible integer roots are which narrows it down considerably. It doesn't take long to see that works.

So nope, not really. You'll have to guess. Unless you want to learn the cubic formula off by heart, but... yeah.
(Original post by kanzev)
Ruffini's rule, which is the method described by the user before me.
Thank you!!
5. (Original post by Zacken)
Rational root theorem tells us that the only possible integer roots are which narrows it down considerably. It doesn't take long to see that works.

So nope, not really. You'll have to guess. Unless you want to learn the cubic formula off by heart, but... yeah.
I don't think anyone remembers the cubic formula in terms of the coefficients of the cubic equation, that would be painful as I'm sure you're aware. I know how to do it by a series of substitutions (probably the way everyone has learnt it) and then working back from there. Gives you nasty answers before cleaning up.
6. (Original post by Ano123)
I don't think anyone remembers the cubic formula in terms of the coefficients of the cubic equation, that would be painful as I'm sure you're aware. I know how to do it by a series of substitutions (probably the way everyone has learnt it) and then working back from there. Gives you nasty answers before cleaning up.
Yes, it was tongue-in-cheek.

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