/////////////////////
x₀=1; f'(x)=((2x³-4x²)/(3x-1))'=((6х²-8х)*(3х-1)-3*(2x³-4x²))/(3x-1)²)=
(18х³-6х²-24х²+8х-6х³+12х²)/(3x-1)²=(12х³-18х²+8х)/(3x-1)²
f'(1)=(12-18+8)/(3-1)²=2/4=0.5
