Tue May 08, 2012 By:

let A={1,{1},2,{1,2},2} then state if it is true or not {2,1}is a subset of A?

Expert Reply
Tue May 08, 2012
Let S = {a, b, c, d}. Then the subsets:
the 1-combinations are : {a}, {b}, {c}, {d}
the 2-combinations are : {a, b}, {a, c}, {a, d}, {b, c}, {b, d}, {c, d}
the 3-combinations are : {a, b, c}, {a, b, d}, {a, c, d}, {b, c, d}
the 4-combination is : {a, b, c, d}.
Hence A={1, {1}, 2, {1, 2}}
Subsets will be -
{1,{1}}; {1,2}; {1,{1,2}}; {{1},2};{{1},{1,2}}; {2,{1,2}}
Also the elements may be listed in any order.
Therefore, {2, 1} is a subset of A.
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