Mathematical Proofs And Induction: Set Theory, Even/Odd Properties, And Sum Of Cubes
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Mathematical Proofs and Induction: Set Theory, Even/Odd Properties,and Sum of CubesJeremy BreitMarch 25, 2013MTH 231Homework #2Problem:Prove that, for all integers n, if n2+ 3 is even, then n is odd.Solution:1. Assuming n2+ 3 is even, we can say that 2 divides the equation. n2+ 32|(π2+3)βΊπ2+3=2πππππ πππππβ€Simply,π2+3is some integer multiple of 2.2. Since 2(k-2) is divisible by 2, and 2 is not divisible by 1, we can say thefollowing:π2=2πβ3=2(πβ2)+1βΉ2ππππ πππ‘πππ£πππ2(πβ2)+1,βΉ2ππππ πππ‘πππ£ππππ2Simply, since 2 does not divideπ2,π2cannot be even. This means thatπ2is odd.3. Next we need to prove that sinceπ2is odd,πis therefor odd. To do this, wewill prove the contrapositive. In this case, we will assumeπis even.π=2πππππ ππππππ‘πππππTherefor,π2=(2π)2=2(2π2)4. Since 2 dividesπ2,π2must be even. Therefor, is n is not odd,π2is not odd aswell.5. Contrapositively, sinceπ2is odd,πmust be odd as well.
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