lim(n→∞)(3n^2-n+1)/(2+n^2)
=lim(n→∞)(3n^2+6-6-n+1)/(2+n^2)
=lim(n→∞)[3(n^2+2)-(5+n)]/(2+n^2)
=lim(n→∞)[3-(5+n)/(2+n^2)]
=3