1) 9-8х-x^2≥0
-x^2-8x+9=0; D=b^2-4ac; D=64-4*(-1)*9=64+36=100=10^2;
x1=(-b-√D)/(2a)=8-10)/(-2)=1; x2=(8+10)/(-2)=-9
- + -
------------------ -9------------- 1--------------->x
///////////////////// x⊂[-9;1]
D(F)=[-9;1]
2)Рассмотрим f(x)=(x+1)(x-8)(3x+2), x≠8; x≠-2/3
- + - +
----------------- -1---------- -2/3------------8------------->x
//////////////////////// ////////////////////
x⊂(-∞;-1]∪(-2/3;8)