If I have finite sets X,Y, and need to prove that X ⊆ Y <=> P(X) ⊆ P(Y), where P() denotes the power set of a set.
I started out saying that for infinite sets X,Y, x⊆X, and y⊆Y.
Given that X⊆Y, we want to show that P(B)⊆P(Y).
x⊆X, so through transitivity, x⊆Y (is this correct?). From here, I...