Question 1186668: If p={1,2,3.4},Write down all the subsets of p which have exactly two element
Found 2 solutions by MathLover1, greenestamps:
Answer by MathLover1(20850)   (Show Source):
You can put this solution on YOUR website!
{},{1},{2},{3},{4},{1,2},{1,3},{2,3},{1,4},{2,4},{3,4},{1,2,3},{1,2,4},{1,3,4},{2,3,4},{1,2,3,4}
Subsets: total 
Proper Subsets total: 
 subset with no elements
 subset with elements
 subset with elements
subset with  elements
subset with elements
you need subset with elements: {1,2},{1,3},{2,3},{1,4},{2,4},{3,4}
Answer by greenestamps(13200)  (Show Source):
You can put this solution on YOUR website!
You need to choose 2 of the 4 elements; the number of ways you can do that is "4 choose 2" = C(4,2) = 6.
You can make the list; it should have 6 different subsets.
To make sure you don't count any subset twice, make sure each subset you write has the smaller of the two elements first -- that is, for example, you don't want to have two different subsets {2,4} and {4,2}, because those are the same.
Or of course you could make sure that in each subset you list the larger of the two numbers is first....
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