подставляем (3*0,12-4*1.28)-(2*0.12-3*1.28)
(0.36-5.12)-(0.24-3.84)=(-4.76)-(-3,6)
-*(-3.6)=3.6=-4.76+3.6=-1.16
D=144-4*30=144-120=24
x1=(-12+√24)/2=(-12+2√6)/2=-6+√6
(x1)²=(-6+√6)²=36-12√6+6
x2=(-12-√24)/2=(-12-2√6)/2=-6-√6
(x2)²=36+12√6+6
(x1)²+(x2)²=36-12√6+6+36+12√6+6=72+12=84
(x-y)-a(y-x) =(x-y)+a(x-y) =(x-y)(1+a)