(6.2х+9.3)*(4х-3.6)=0

получаим уравнение 
  24.8*x^2+14.88*x-33.48=0

D=14.88^2-4*24.8*(-33.48)=(138384//625)-4*24.8*(-33.48)=(138384//625)-99.2*(-33.48)=(138384//625)-(-99.2*33.48)=(138384//625)-(-3321.216)=(138384//625)+3321.216=2214144//625~~3542.6304

x_1=(2root(2214144//625)-14.88)/(2*24.8)=(59.52-14.88)/(2*24.8)=44.64/(2*24.8)=44.64/49.6=0.9;
x_2=(-2root(2214144//625)-14.88)/(2*24.8)=(-59.52-14.88)/(2*24.8)=-74.4/(2*24.8)=-74.4/49.6=-1.5.