lim(n→∞) [1+(2nx+x²)/2n²]^(-n)=lim(n→∞) [1+(2nx+x²)/2n²]^{[2n²/(2nx+x²]*[2nx+x²)/2n²]*(-n)}=e^lim(n→∞) [2nx+x²)/2n²]*(-n)=e^(-x)
