1.lim (2^n-3^n)/(2^(n+1)+3^(n+1))上下同除3^n=lim ((2/3)^n-1)/(2*(2/3)^n+3)=(0-1)/(0+3)=-1/32.lim (x-sinx)/(x+sinx)上下同除x=lim (1-sinx/x)/(1+sinx/x)=(1-0)/(1+0)=1有不懂欢迎追问