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maths: algebraic proof

prove that the sum of the squares of two consecutive odd numbers is always 2 more than a multiple of 8
Reply 1
Let k be an integer. Then (2k+1)^2+(2k+3)^2 = 4k^2 + 4k + 1 + 4k^2 + 12k + 9 = 8(k^2 + 2k +1) + 2
Since k is an integer, (k^2 + 2k +1) is an integer, so 8(k^2 + 2k +1) is a multiple of 8 and thus the sum of the squares of 2 consecutive odd integers is 2 greater than a multiple of 8

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