64х^3+144х^2+108х+27=0
64х^3+48х^2+96х^2+72х+36х+27=0
16х^2*(4х+3)+24х*(4х+3)+9*(4х+3)=0
(4х+3)*(16х^2+24х+9)=0
(4х+3)*(4х+3)^2=0
(4х+3)^3=0
4х+3=0
4х=-3
х=-3/4=-0,75
Формула :
a^2-b^2 = (a-b)(a+b)
(17/15-1/12)*20/3=(17*12-15)/(15*12)*20/3=(189/180)*20/3=7