1
a)
{(x-1)(3x-6)≥0⇒x≤1 U x≥2
{x²+4x-21≠0⇒x≠-7 U x≠3
x1+x2=-4 U x1*x2=-21⇒x1=-7 U x2=3
x∈(-∞;-7) U (-7;1] U [2;3) U (3;∞)
б)
{|x|-5≠0⇒|x|=5⇒x≠-5 U x≠5
{79-x²>0⇒(√79-x)√79+x)>0⇒-√79x∈(-√79;-5) U (-5;5) U (5;√79)
2
(x²+2x-24)/(x+4)²≤0
x²+2x-24=0
x1+x2=-2 U x1*x2=-24⇒x1=-6 U x2=4
x+4=0⇒x=-4
+ _ _ +
------------[-6]------------(-4)-----------[4]---------------
x∈[-6;-4) U (4;4]
-6-5-3-2-1+0+1+2+3+4=-7
3
y=-3/(x²+5)
E(y)∈(-∞;0)