Let f (x) = x4 + x3 + x2 + x + 1 ∈ Z2[x]. Prove that f(x) is irreducible over Z2[x] or not?

Answer and Step-by-step explanation:

Let f(x) = x4 + x3 + x2 +x + 1 Є Z2[x]. Prove that f(x) is irreducible over Z2[x] or not?

Proof:-  

Let f(x) = x4 + x3 + x2+ x+1 Є Z2[X].  

Then f (0) = 1 = f(1), so f(x) has no roots,  By Factor theorem, which states that polynomial f(x) has a factor(x-a) if and only if f(a)=0.                                                                                                                                      Hence, f(x) has no linear factor.                                                                                                                                                 If f(x) is reducible, it must have factors of degree 2 and degree 3. But f(x) has no degree 2 factors.

We know that only irreducible quadratic in Z2[X] is x2  + x +1. When we divide f(x) by x2  + x +1 we get a remainder of 1, so x2  + x +1 is not a factor of f(x) therefore f(x) is irreducible.

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