(x-4)(x-5)(x-6)=(x-2)(x-5)(x-6)
(x²-9x+20)(x-6)= (x²-7x+10)(x-6)
x³-6x²-9x²+54x+20x-120=x³-6x²+7x²+42x+10x-60
-9x²+74x-120= -7x²+42x+10x-60
-9x²+74x-120+7x²-52x+60=0
-2x²+22x-60=0
x²-11x+30=0
D=121-120=1
x1=11+√1 / 2=11+1 / 2=12/2=6
x2=11-√1 / 2=11-1 / 2=10/2=5
Ответ: х1=6
х2=5