√n[√(n+1)-√n]
=√n[√(n+1)-√n][√(n+1)+√n]/[√(n+1)+√n]
=√n/[√(n+1)+√n]
lim(n→∞)√n[√(n+1)-√n]
=lim(n→∞)√n/[√(n+1)+√n]
=1/2