Tìm các giới hạn sau: lim ( 2n +1) ^2 ( 3/ n^2 +2n - 1/ n^2 +3n -1 )

lim2n+123n2+2n−1n2+3n−1

=lim32n+12n2+2n−lim2n+12n2+3n−1.

Mà 

 lim32n+12n2+2n=lim32+1n21+2n=3.221=12.

 lim2n+12n2+3n−1=2+1n21+3n−1n2=221=4.

Nên

 lim2n+123n2+2n−1n2+3n−1=12−4=8.