Giải thích các bước giải:
$\lim\dfrac{(2n^2-3n)^{2013}(2n-5)^2}{(4n-1)^{1998}(n^2+3n)^{1015}}$
$=\lim\dfrac{(2-\dfrac 3n)^{2013}(2-\dfrac 5n)^2}{(4-\dfrac 1n)^{1998}(1+\dfrac 3n)^{1015}}$
$=\dfrac{2^{2013}.2^2}{4^{1998}.1^{1015}}$
$=\dfrac{2^{2015}}{2^{3996}}$
$=\dfrac 1{2^{1981}}$