Read: Beginning of Section 3.1.
Turn in: 2.91, 3.2, 3.3, 3.5, 3.7, 3.10
- Even though you’re not being asked to turn in 2.89, please try it, and definitely read the discussion in the text that follows it.
- To clarify the directions for 3.2, here are two possible answers for part (a): Answer 1: $A = \{3,6,9,12,\ldots\}$. Answer 2: $A$ is the set of all natural numbers that are divisible by $3$.
- For 3.7, you should find that there are 8 different subsets.
- Please read Theorem 3.8. It is a small but subtle point.
- Before proving 3.10, make sure to read the text before Problem 3.9. Your goal in 3.10 is to prove $A\subseteq C$. So, using the additional hypotheses, you want to prove that for all $x\in A$, it follows that $x\in C$. As such, your proof should begin with “Let $x\in A$” and end with “Thus, $x\in C$.”
Extra practice: 2.89
