i just started my second semester with geomtry and am having difficulties with these proofs. i am stuck on this one question which asks:(adsbygoogle = window.adsbygoogle || []).push({});

prove that if n is an odd positive integer, then one of the numbers n+5 or n+7 is dividsible by 4.

so this is what i came up with:

let n = 2k+1

f(n)= n+5

= (2k+1)+5

= 2k+6

= 2(k+3)

So we know that 2 is divisible by 2 and now im guessing i have to prove that (k+3) is divisible by 2 as well. then by using the factor tree thing we can say that since the 2 is divisible by 2 and (k+3) is divisible by 2, f(n) must be divisible by 4, no? but i dont get how to do this... am i doing something wrong?

i did the same exact method with f(n)= n+7 and ended up with f(n)= 2(k+4).

i just dont get all this proving stuff.

Any help would be appreciated, thanks.

- Tu

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# Homework Help: Help with proofs

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