Is x^4+x^3+1 Irreducible in Q[x] and Z[x]?

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In summary, factorisation is the process of breaking down a polynomial into smaller polynomials known as factors, which helps to simplify complicated polynomials, solve equations, and identify roots. The main difference between factorisation in Q[x] and Z[x] is the coefficients used, with Q[x] allowing any rational number and Z[x] restricting to integers. To factorise a polynomial, we look for common factors and use techniques such as grouping and trial and error. However, not all polynomials in Q[x] and Z[x] can be factorised, as some may not have any factors or have only complex factors, making them irreducible.
  • #1
Joe20
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Hi all, appreciate your help to look through my answers to see if they are correct.

Thank you.
 

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  • #2
Looks good to me. If you wanted to avoid the long division, you could observe that the only candidate for a quadratic divisor of $\overline{f}(x)$ is $x^2+x+1$ (since you have already ruled out the other three quadratic polynomials). So the only possible factorisation would be if $x^4+x^3 + 1 = (x^2+x+1)^2$. But $(x^2+x+1)^2 = x^4+x^2 + 1 \ne x^4+x^3 + 1$. It follows that $x^4+x^3 + 1$ is irreducible.
 

FAQ: Is x^4+x^3+1 Irreducible in Q[x] and Z[x]?

1. What is factorisation in Q[x] and Z[x]?

Factorisation is the process of breaking down a polynomial into smaller polynomials, known as factors, that when multiplied together, produce the original polynomial.

2. Why is factorisation important in Q[x] and Z[x]?

Factorisation allows us to simplify complicated polynomials and solve equations more easily. It also helps us identify the roots of a polynomial, which are the values that make the polynomial equal to zero.

3. What is the difference between factorisation in Q[x] and Z[x]?

The main difference between factorisation in Q[x] and Z[x] is the coefficients used. In Q[x], the coefficients can be any rational number, while in Z[x], the coefficients are restricted to integers.

4. How do you factorise a polynomial in Q[x] and Z[x]?

To factorise a polynomial in Q[x] and Z[x], we first look for any common factors among the terms. Then, we use various techniques such as grouping, difference of squares, and trial and error to factor the polynomial into smaller polynomials.

5. Can all polynomials in Q[x] and Z[x] be factorised?

No, not all polynomials in Q[x] and Z[x] can be factorised. Some polynomials may not have any factors or may only have complex factors. In these cases, the polynomial is considered to be irreducible and cannot be broken down into simpler polynomials.

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