Im on my last problem and i i know the first one implies the 2nd, the 2nd implies the 3rd and the 3rd implies the first but i keep screwing up somewhere.

i : x2(squared) is odd

ii: 1-x is even

iii: x2 +1 is even

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- Oct 18th 2009, 07:05 PMsprint10schain of equivalants
Im on my last problem and i i know the first one implies the 2nd, the 2nd implies the 3rd and the 3rd implies the first but i keep screwing up somewhere.

i : x2(squared) is odd

ii: 1-x is even

iii: x2 +1 is even - Oct 18th 2009, 07:34 PMtonio
- Oct 19th 2009, 04:05 AMoldguynewstudentdefintion of odd even
if x^2 is odd then x is odd; let x = 2k +1

then x^2 = (2k+1)(2k+1) = 4k^2 + 4k + 1

1 - (4k^2 + 4k + 1) = -4k^2 - 4k = 2(-2k^2 - 2k) which is of the form 2k which proves it's even

(4k^2 + 4k + 1) + 1 = 4k^2 + 4k + 2 = 2(2k^2 + 2k + 1) which again is of the form 2k which proves it's even.