Đáp án:
Kết luận câu b: $S=(-∞;-2/5)$U$(4;+∞)$
$b) |3x-5|≥2x+7$
$⇔$$\left \{ {{3x-5≥2x+7} \atop {3x-5≤-2x-7}} \right.$ $⇔$ $\left \{ {{3x-5-2x-7≥0} \atop {3x+2x-5+7≤0}} \right.$
$⇔$ $\left \{ {{3x-12≥0} \atop {5x+2≤0}} \right.$ $⇔$ $\left \{ {{3x≥12} \atop {5x≤-2}} \right.$ $⇔$ $\left \{ {{x≥4} \atop {x≤-2/5}} \right.$
$⇒ x∈(-∞;-2/5)$U$(4;+∞)$
Vậy $S=(-∞;-2/5)$U$(4;+∞)$
BẠN THAM KHẢO NHA!!!
