Mathematics for IGCSE & O level - Sets (Section 3 - No. 34)
If A is a subset of B (A ⊆ B), what does this mean?
All elements of A are also in B
All elements of B are also in A
A and B have no elements in common
A contains more elements than B
説明
A ⊆ B means every element in set A is also in set B.