5x^2-18x-8<=0
D=324+4*5*8=324+160=468
x1=(18+V468)/10=(18+6V13)/10=(9+3V13)/5
x2=(9-3V13)/5
x€[(9-3V13)/5; (9+3V13)/5]
5x^2-18x-8<=0
D=324+4*5*8=324+160=468
x1=(18+V468)/10=(18+6V13)/10=(9+3V13)/5
x2=(9-3V13)/5
x€[(9-3V13)/5; (9+3V13)/5]