1)1/9х²-х+2=0
D = b 2 - 4ac = -7, D < 0 => 2 комплексных решения, √|D| = 2,6457513110646
х₁=-b+i*√D/2a=1+i*2,6457513110646/2*(1/9)=0,5+i*1,3229;
х₂=-b-i*√D/2a=1-i*2,6457513110646/2*(1/9)=0,5-i*1,3229
2)с²+4с+4/с²-4 :(с+2)= (с+2)²*1/(с+2)(с-2)*(с+2) = (с+2)²*1/(с+2)²(с-2)=1/(с-2)
3)left \{ {{2x+3>3x} \atop {1+2x<0}} \right</p>
left \{ {{x<3} \atop {x<-1/2}} \right</p>