Subset Math Example 2

Follow the full solution, then compare it with the other examples linked below.

Example 2

medium
List all subsets of S={a,b,c}S = \{a, b, c\}.

Solution

  1. 1
    A set with nn elements has exactly 2n2^n subsets (including โˆ…\emptyset and the set itself). Here โˆฃSโˆฃ=3|S| = 3, so there are 23=82^3 = 8 subsets.
  2. 2
    List subsets by size systematically โ€” size 0: โˆ…\emptyset. Size 1: {a},{b},{c}\{a\}, \{b\}, \{c\}. Size 2: {a,b},{a,c},{b,c}\{a,b\}, \{a,c\}, \{b,c\}. Size 3: {a,b,c}\{a,b,c\}.
  3. 3
    Verify the count: 1+3+3+1=8=231 + 3 + 3 + 1 = 8 = 2^3 โœ“. These 8 sets form the power set P(S)\mathcal{P}(S).

Answer

โˆ…,โ€…โ€Š{a},โ€…โ€Š{b},โ€…โ€Š{c},โ€…โ€Š{a,b},โ€…โ€Š{a,c},โ€…โ€Š{b,c},โ€…โ€Š{a,b,c}\emptyset,\; \{a\},\; \{b\},\; \{c\},\; \{a,b\},\; \{a,c\},\; \{b,c\},\; \{a,b,c\}
The power set of SS contains every possible subset, including the empty set and SS itself. For a set of size nn, there are always 2n2^n subsets.

About Subset

Set AA is a subset of set BB if every element of AA is also an element of BB, written AโІBA \subseteq B.

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