Determine if this polynomial has a repeated factor

  • Thread starter Firepanda
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In summary, f(t) = t4 - 23 + 3t2 - 2t + 1 in Q[t] is an irreducible polynomial as it has no rational roots and therefore no linear factors with rational coefficients.
  • #1
Firepanda
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f(t) = t4 - 23 + 3t2 - 2t + 1 in Q[t]

Am i right in thinking I just show by the rational root theorem that the only possible roots are +-1

f(+-1) =/= 0 so there are no repeated factors?

Seems too easy..
 
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  • #2
Firepanda said:
f(t) = t4 - 23 + 3t2 - 2t + 1 in Q[t]

Am i right in thinking I just show by the rational root theorem that the only possible roots are +-1
No. Your work shows there are no rational roots, but there could be real or complex roots.

Are you limiting your search only to rational numbers? I'm not sure what your Q[t] notation means, although it suggests to me polynomial functions of t with rational coefficients. Correct me if I have misinterpreted this.
Firepanda said:
f(+-1) =/= 0 so there are no repeated factors?

Seems too easy..
 
  • #3
Mark44, I would interpret Q(t) to mean the set of polynomials in t with rational coefficients. A polynomial is "factorable in Q(t)" if and only it is the product of factors with rational coefficients.
Since a cubic, if factorable, must have at least one linear factor, Firepanda is quite correct in noting that, since the polynomial has no rational roots, it has no linear factor with rational coefficients and so is irreducible in Q(t).
 

FAQ: Determine if this polynomial has a repeated factor

What is a repeated factor in a polynomial?

A repeated factor in a polynomial is a factor that appears more than once in the polynomial. For example, in the polynomial 2x^2 + 4x + 2, the factor (x+1) appears twice, making it a repeated factor.

How can I determine if a polynomial has a repeated factor?

To determine if a polynomial has a repeated factor, you can factor the polynomial and look for factors that appear more than once. Another way is to check the degree of each factor - if it is greater than 1, it is a repeated factor.

Why is it important to know if a polynomial has a repeated factor?

Knowing if a polynomial has a repeated factor can help in simplifying the polynomial and finding its roots. Repeated factors can also provide information about the behavior of the polynomial and can help in graphing it.

Can a polynomial have more than one repeated factor?

Yes, a polynomial can have more than one repeated factor. For example, the polynomial (x+1)^3 would have the repeated factor (x+1) three times.

What should I do if I find a repeated factor in a polynomial?

If you find a repeated factor in a polynomial, you can use the repeated factor theorem to simplify the polynomial and find its roots. This theorem states that if a polynomial has a repeated factor, the root associated with that factor will have a multiplicity greater than 1.

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