lim (+oo) (4n^3-5n^2-4)/(5n^3+12n^2+13)= lin (+oo) (4-5/n-4/n^3)/(5+12/n+13/n^3) = 4/5
делим верх-низ на n^3
lim (+oo) (4n^3-5n^2-4)/(5n^3+12n^2+13)= lin (+oo) (4-5/n-4/n^3)/(5+12/n+13/n^3) = 4/5
делим верх-низ на n^3