b) (x – 1)(x + 1)(x^2 + 1)(x^4 + 1).
Giải thích
b) (x – 1)(x + 1)(x2 + 1)(x4 + 1)
= [(x – 1)(x + 1)](x2 + 1)(x4 + 1)
= (x2 ‒ 1)(x2 + 1)(x4 + 1)
= [(x2 ‒ 1)(x2 + 1)](x4 + 1)
= [(x2)2 ‒ 12](x4 + 1)
= (x4 ‒ 1)(x4 + 1)
= (x4)2 ‒ 1 = x8 ‒ 1.
b) (x – 1)(x + 1)(x2 + 1)(x4 + 1)
= [(x – 1)(x + 1)](x2 + 1)(x4 + 1)
= (x2 ‒ 1)(x2 + 1)(x4 + 1)
= [(x2 ‒ 1)(x2 + 1)](x4 + 1)
= [(x2)2 ‒ 12](x4 + 1)
= (x4 ‒ 1)(x4 + 1)
= (x4)2 ‒ 1 = x8 ‒ 1.