aminak185
01.03.2021 •
Mathematics
Hi guys
please help
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Ответ:
- 1
Step-by-step explanation:
Multiplying a negative quantity by a negative quantity results in a positive.
Also multiplying by 1 leaves the other value as is, then
- 1 × - =
Ответ:
We are to show that if X ⊆ Y then (X ∪ Z) ⊆ (Y ∪ Z) for sets X, Y, Z.
Assume that a is a representative element of X, that is, a ∈ X. By the definition of union, a ∈ X ∪ Z. Now because X ⊆ Y and we assumed a ∈ X, then a ∈ Y by the definition of subset. And because a ∈ Y, then a ∈ Y ∪ Z by definition of union.
We chose our representative element, a, and showed that a ∈ X ∪ Y implies that a ∈ Y ∪ Z and this completes the proof.