Unformatted text preview: f is surjective onto B and g ◦ f is injective then g is injective. 8 Prove by induction that n ! > 2 n for all n ≥ 4. 9 Prove that if A ≈ B then A × A ≈ B × B . 10 Label the following sets ﬁnite, countably inﬁnite, or uncountably inﬁnite. You don’t have to prove anything. (a) ∅ (b) Z (c) Z × Z (d) The set of all functions from Z to R (e) The set of all stars in the galaxy. 1...
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 Fall '08
 Bigelow
 Math, Countable set, English sentence

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