Bài 1:
$|x+5|≤2$
$⇔-2≤x+5≤2$
$⇔-7≤x≤-3$
Bài 2:
$(x²-20)(x²-15)(x²-10)(x²-5)<0$
Ta thấy: $(x²-20)<(x²-15)<(x²-10)<(x²-5)$
$⇒\left \{ {{x²-15<0} \atop {x²-10>0}} \right.$
$⇔\left \{ {{x²<15} \atop {x²>10}} \right.$
$⇒10<x²<15$
$⇔\left[ \begin{array}{l}\sqrt{10}<x<\sqrt{15}\\-\sqrt{10}>x>\sqrt{15}\end{array} \right.$