# Math Help - Proving unions by Algebra of Sets

1. ## Proving unions by Algebra of Sets

Yikes...help please if you can:
1. Prove B-(A U B)=0 Note "0" here is the empty set

2. Prove if A Intersect B =A, then A is a subset of B Note: This is not to be proven by Algebra of Sets, rather treated as a proof of a biconditional proposition.

2. Originally Posted by IIuvsnshine
Yikes...help please if you can:
1. Prove B-(A U B)=0 Note "0" here is the empty set
.
If $x\in B$ then $x\in (A\cup B)$ so $B$ has all its elements in $A\cup B$ so the set difference is zero.