Question

用描述法表示集合 {2,4,6,8} {1,1/2,1/3,1/4}

Answer 1

{2,4,6,8}={x I x=2n,1≤n≤4,n∈N}

{1,1/2,1/3,1/4}={x I x=1/n,1≤n≤4,n∈N}