2n—根号（4n^2-kn+3）=(kn-3)/(2n+根号（4n^2-kn+3))lim 2n—根号（4n^2-kn+3）=lim(kn-3)/(2n+根号（4n^2-kn+3))=lim(k-3/n)/(2+根号（4-k/n+3/n^2))=(k-0)/(2+根号（4-0+0））=k/4=1k=4