9x+9x²<4;
9x+9x²-4<0;⇒
9x²+9x-4=0;
x₁,₂=(-9⁺₋√(81+4·9·4))/18=(-9⁺₋√225)/18=(-9⁺₋15)/18;
x₁=(-9+15)/18=1/3;
x₂=(-9-15)/18=-24/18=-1¹/₃;
9x²+9x-4=9(x-1/3)(x+1¹/₃);
9(x-1/3)(x+1¹/₃)<0;
(x-1/3)(x+1¹/₃)<0;
(x-1/3)<0; (x+1¹/₃)>0;⇒
x<1/3; x>-1¹/₃⇒
-1¹/₃<x<1/3;
15*20=х*1/4
300=1/4х
х=300*4
х=1200
0,24х + 72 - 0,94х = 163
- 0,7х = 163 - 72
- 0,7х = 91
х = 91 : (- 0,7)
х = - 130