tìm giới hạn dãy số
1)lim(√n+5n+1n+5n+1 - √n2−nn2−n )
2)lim√3n2+2n−13n2+2n−1 - √3n2−4n+83n2−4n+8
3)lim3n−4+5n3n+4n−5n3n−4+5n3n+4n−5n
4)lim2n+6n−4n+13n+6n+12n+6n−4n+13n+6n+1
5)lim1+3+5+....+(2n+1)32+41+3+5+....+(2n+1)32+4
6)lim[11.211.2+ 12.312.3+...+ 1n(n+1)1n(n+1) ]
7)lim12+22+32+...+n2n(n+1)(n+2)