Question

Let x^8+3x^4-4=p_1(x)p_2(x)...p_k(x) where each non-constant polynomial p_i(x) is monic with integer coefficients, and cannot be factored further over the integers. Compute p_1(1)+p_2(1)+...+p_k(1).

Answer 1

Answer: We can factor the given polynomial as follows:

x^8 + 3x^4 - 4 = (x^4 - 1)(x^4 + 4)

= (x^2 - 1)(x^2 + 1)(x^2 - 2x + 1)(x^2 + 2x + 1)

The four factors on the right-hand side are all monic polynomials with integer coefficients that cannot be factored further over the integers. Therefore, we have k = 4, and we can compute p_1(1) + p_2(1) + p_3(1) + p_4(1) as follows:

p_1(1) + p_2(1) + p_3(1) + p_4(1) = (1^2 - 1) + (1^2 + 1) + (1^2 - 2(1) + 1) + (1^2 + 2(1) + 1)

= 0 + 2 + 0 + 6

= 8

Therefore, p_1(1) + p_2(1) + p_3(1) + p_4(1) = 8.

Explanation: