5.
x²+6x-16=0
D=36+64=100
x₁=(6-10)/2= -2
x₂=(6+10)/2=8
+ - +
------ -2 --------- 8 ---------------
\\\\\\\\\\ \\\\\\\\\\\\\\\\\\\\\
x∈(-∞; -2]U[8;+∞)
6.
2x-7≤x-12
2x-x≤-12+7
x≤ -5
4x-5≥3x-20
4x-3x≥-20+5
x≥-15
{x≤-5
{x≥-15
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
-------- -15 ----------- -5 -------------
////////////////////////////////
x∈[-15; -5]