The number of elements in a power set of size <= 1 is the size of the original set + 1 more element: the empty set .
Suppose      ∣A∣=m|A|=m∣A∣=m  . What is the size of this set:      ∣{X∈P(A)∈:∣X∣≤1}∣ | \{X \in \maths...
Tags: math, sets