Đáp án+Giải thích các bước giải:

 Gọi `f(x) = (x-1)(x^2-4)`

Cho `f(x) = 0`

$⇒\left[\begin{matrix} x=1\\ x=± 2\end{matrix}\right.$

BXD :\begin{array}{|c|c|c|}\hline \text{x}&\text{-∞}&\text{-2}&\text{}&\text{1}&\text{}&\text{2}&\text{+∞}\\\hline \text{x-1}&\text{-}&\text{|}&\text{-}&\text{0}&\text{+}&\text{|}&\text{+}\\\hline \text{x^2 -4}&\text{+}&\text{0}&\text{-}&\text{|}&\text{-}&\text{0}&\text{+}\\\hline \text{f(x)}&\text{-}&\text{0}&\text{+}&\text{0}&\text{-}&\text{0}&\text{+}\\\hline\end{array}

`=>` `f(x) >= 0`

`⇔``x\in [-2;1] ∪ [2;+ ∞)`