Răspuns:
x ∈ [1 , +∞) ∪ {-1}
Explicație pas cu pas:
(x²-1)·(x+1) ≥ 0 ; x = ?
____________
<=> (x-1)(x+1)(x+1) ≥ 0
x-1 = 0 => x = 1 ; x+1 = 0 => x = -1
x I -∞ -1 1 +∞
________________________________
x-1 I --------------------------------0+++++++++++
x+1 I----------------------0++++++++++++++++++
x+1 I----------------------0++++++++++++++++++
(x-1)(x+1)(x+1) I----------------------0---------0+++++++++++
=> x ∈ [1 , +∞) ∪ {-1}
