3x²-8x-4=3(x²-2*x*4/3+16/9)-3*16/9 -4=3(x-4/3)²-28/3=0
3(x-4/3)²=28/3
(x-4/3)²=28/9
x-4/3=-2√7/3⇒x=4/3-2√7/3=(4-2√7)3
x-4/3=2√7/3⇒x=(4+2√7)3
Проверка
3x²-8x-4=0⇒x1+x2=8/3 U x1*x2=-4/3
x1+x2=4/3-2√7/3+4/3+2√7/3=8/3
x1*x2=(4/3-2√7/3)(4/3+2√7/3)=16/9-28/9=-12/9=-4/3