1
(x-2)(x+2)(x+3)/(x+1)²≥0
x=2 x=-2 x=-3 x=-1
_ + _ _ +
--------------[-3]--------[-2]----------(-1)------------[2]-----------
x∈[-3;-2] U [2;∞)
2
{xy(x+y)=20
{(x=y)-xy=1
x+y=a xy=b
{ab=20
a-b=1⇒a=1+b
(1+b)b=20
b²+b-20=0
b1+b2=-1 U b1*b2=-20
b1=-5⇒a1=-4
{x+y=-4⇒x=-4-y
{xy=-5
y(-4-y)=-5
y²+4y-5=0
y1=y2=-4 U y1*y2=-5
y1=-5⇒x1=1
y2=1⇒x2=-5
b2=4⇒a2=5
{x+y=5
{x*y=4
по теореме Виета х=1,у=4 или х=4,у=1
Ответ (1;-5);(-5;1);(1;4);(4;1)
4
3x²+bx+12=0
D=b²-144<0<br>(b-12)(b+12)<0<br>b=12 b=-12
b∈(-12;12)