For any two sets A and B, show that the following statements are equivalent:
A ⊂ B
To show that the following four statements are equivalent, we need to show that 1⇒2, 2⇒3, 3⇒ 4, 4⇒1
We first show that 1⇒ 2
Now A–B = {xϵ A: x ∉ B} .As A ⊂ B,
∴ Each element of A is an element of B,
∴ A–B = ϕ
Hence we proved 1⇒ 2.