n/(n+2)=(n+2-2)/(n+2)=1-2/(n+2)令-2/(n+2)=1/a则n=-2a-2所以[n/(n+2)]^n=(1+1/a)^(-2a-2)=[(1+1/a)^a]^(-2)*(1+1/a)^(-2)(1+1/a)^(-2)极限是1(1+1/a)^a极限是e所以圆极限=e^(-2)