Объяснение:

2.

[tex]3x+6 < 0\\3x < -6\ |:3\\x < -2.\\x\in(-\infty;-2).[/tex]

Ответ: A) (-∞;-2).

3.

[tex]\left \{ {{x^2+y^2=10} \atop {y-2x=5}} \right. \ \ \ \ \left \{ {{x^2+(2x+5)^2=10} \atop\ \ \ \ \ {y=2x+5}} \right. \ \ \ \ \ \left \{ {{x^2+4x^2+20x+25=10} \atop {y=2x+5}} \right. \ \ \ \ \ \left \{ {{5x^2+20x+15=0\ |:5} \atop {y=2x+5}} \right.[/tex]

[tex]\left \{ {{x^2+4x+3=0} \atop {y=2x+5}} \right.\ \ \ \ \ \left \{ {{D=4\ \ \ \sqrt{D}=2 } \atop {y=2x+5}} \right.\ \ \ \ \ \left \{ {{x_1=-3\ \ \ \ x_2=-1} \atop {y_1=-1}\ \ \ \ \ y_2=3} \right..[/tex]

Ответ: Г) (-3;-1).

4.

[tex]x^2-3x-4 > 0\\x^2-4x+x-4 > 0\\x*(x-4)+(x-4) > 0\\(x-4)*(x+1) > 0.[/tex]

-∞__+__-1__-__4__+__+∞

Ответ: x∈(-∞;-1)U(4;+∞).