x3 + x2 + x + 1 = 0
<=> x(x2 + x ) + 1=0
<=> x2 (x + 1) + 1 = 0
<=> [x2 = 0 <=> [ x = 0
<=> [(x + 1) + 1 = 0 <=> x = - 2
2x3 + 2x2 + 2x + 3 = 0
<=> 2x (x2 + x + 1) + 3 = 0
<=> 2x (x + 1)2 + 3 = 0
<=> [2x = 0 <=> [x = - 2
<=> [ (x + 1)2 + 3 <=> [ x = - 4