Ta có : x5 + x + 1
= x5 + x4 + x3 + x2 + x + 1 - x4 - x3 - x2
= (x5 + x4 + x3) + (x2 + x + 1) - (x4 + x3 + x2)
= x3(x2 + x + 1) + (x2 + x + 1) - x2(x2 + x + 1)
= (x2 + x + 1)(x3 - x2 + 1) .
Ta có : x5 + x + 1
= x5 + x4 + x3 + x2 + x + 1 - x4 - x3 - x2
= (x5 + x4 + x3) + (x2 + x + 1) - (x4 + x3 + x2)
= x3(x2 + x + 1) + (x2 + x + 1) - x2(x2 + x + 1)
= (x2 + x + 1)(x3 - x2 + 1) .
= x5 + x4 + x3 + x2 + x + 1 - x4 - x3 - x2
= (x5 + x4 + x3) + (x2 + x + 1) - (x4 + x3 + x2)
= x3(x2 + x + 1) + (x2 + x + 1) - x2(x2 + x + 1)
= (x2 + x + 1)(x3 - x2 + 1) .